I 953 
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NITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 866 

Contribution from the Bureau of Chemistry 
CARL L. ALSBERG, Chief 



Washington, D. C. 



August 24, 1920 



PICKERING SPRAYS 



By 



F. C. COOK, Physiological Chemist 
Insecticide and Fungicide Laboratory 



CONTENTS 



Page 

Introduction 1 

Results of Previous Investigations . . . 2 

Purpose of Present Investigation . . 6 

Preparation of Sprays Used 7 

Results of Investigation : 

Potatoes 8 

Grapes 22 



Page 
Results of Investigation— continued. 

Apples 29 

Cranberries 37 

Suggestions for the Preparation of Pick- 
ering Spray on a Commercial Scale . 42 

Summary 44 

Bibliography 46 




WASHINGTON 
GOVERNMENT PRINTING OFFICE 

1920 




SEP 



Of 3. 

« 1923 



,C2£ 



UNITED STATES DEPARTMENT OF AGRICULTURE 

BULLETIN No. 866 




sl^-'^j-u 



Contribution from the Bureau of Chemistry 
CARL L. ALSBERG, Chief 




■sO^^j-u 



Washington, D. C. 



August 24, 1920 



PICKERING SPRAYS. 

By F. C. Cook, 1 Physiological Chemist, 
Insecticide and Fungicide Laboratory. 



CONTENTS. 



Page. 

Introduction 1 

Results of previous investigations 2 

Purpose of present investigation 

Preparation of sprays used 7 

Results of investigation: 

Potatoes 8 

Grapes 22 



Page 
Results of investigation — Continued. 

Apples 29 

Cranberries 37 

Suggestions for the preparation of Pickering 

spray on a commercial scale 42 

Summary 44 

Bibliography , 40 



INTRODUCTION. 

When, in 1916, the price of copper sulphate (bluestone or blue 
vitriol) rose to 25 and 30 cents a pound in certain parts of the country, 
the United States Department of Agriculture began to receive many 
inquiries as to the possibility of controlling certain fungous diseases 
of fruits and vegetables, either by using sprays other than those 
containing copper or by reducing the amount of copper sulphate 
used per given amount of spray. Past work having failed to show- 
any fungicides which could replace the copper sprays for certain 
important plant diseases and the search for a new spray appearing 
rather unpromising, it seemed advisable to seek a copper spray 
which was more effective per unit of copper than the standard 
Bordeaux mixture and at the same time not so caustic as to injure 
vegetation. Accordingly, the Bureau of Chemistry, in cooperation 
with the Bureau of Plant Industry and the Maine Agricultural Ex- 
periment Station, undertook an investigation to determine the com- 
parative efficacy of the so-called Pickering sprays, which had been 

1 The author wishes to express his appreciation of the cooperation he received from J. K. Haywood,. 
Bureau of Chemistry; from W. B. Clark, H. A. Edson, L. H. Evans, W. A. Orton, J. W. Roberts, E. S. 
Schultz, C L. Shear, M. B. Waite, E. Wallace, and R. B. Wilcox, of the Bureau of Plant Industry; 
from Donald Poison, W. A. Morse, G. B. Ramsey, and C D. Woods, of the Maine Agricultural Experi- 
ment Station; and from Franklin Chambers, Superintendent of Whitesbog, Hanover Farms, N. J., and 
J. E. Sullivan, Superintendent of Aroostook Farm, Maine. 



1S0971 — 20— Bull. 



-1 



2 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

tested to a limited extent in England, where laboratory tests indicated 
that they were superior to the Bordeaux sprays (3, 4). 1 Piekering 
sprays, sometimes called Pickering limewater sprays, are prepared 
by mixing saturated limewater with dilute solutions of copper sul- 
phate, and contain their copper in the form of basic copper sulphates. 

RESULTS OF PREVIOUS INVESTIGATIONS. 
FUNGICIDAL ACTION. 

Bedford and Pickering (3, 4) claimed that the fungicidal action of 
Bordeaux depends upon the re-format ion of copper sulphate by tho 
action of carbon dioxid from the air. They believed that the excess 
of lime present in Bordeaux is carbonated before the copper, and 
held that since the fungicidal action depends upon the carbonation 
of the copper and the re- formation of copper sulphate, the ox< ess 
lime of Bordeaux delays the action. These investigators stated that 
basic sulphates of copper are produced by the action of lime on cop- 
per sulphate, and that the basic sulphates vary in composition 
according to the proportions of lime and copper used. Most of the 
basic sulphates are complex, and contain, in addition to the ele- 
ments essential in a basic sulphate of copper, calcium sulphate or 
calcium oxid, sometimes both. For present purposes the calcium 
sulphate in these compounds need not be considered. The basic 
sulphates of copper, being practically insoluble in water, can of 
themselves have little or no fungicidal action, but when exposed to 
the carbon dioxid of the air they are gradually decomposed to form 
copper carbonate and copper sulphate. The copper carbonate, 
being insoluble, is incapable of energetic action. According to 
Bedford and Pickering, the substances which are formed in the so- 
called Pickering sprays by the action of lime on copper sulphate, 
omitting the calcium sulphate present, are: 

Formula A.— 4 CuO, S0 3 (or 10 CuO, 2.5 S0 3 ). 

Formula B.— 5 CuO, S0 3 (or 10 CuO, 2 S0 3 ). 

Formula C— 10 CuO, S0 3 . 

Formula D. — ■ 10 CuO, S0 3 , 3 CaO (ordinary Bordeaux). 

Formula E.— CuO, 2 CaO (or 10 CuO, 20 CaO) (existence 

doubtful). 
Formula F. r- CuO, 3 CaO (or 10 CuO, 30 CaO). 

The following equations 3 express the changes which these sub- 
stances undergo when acted upon by carbon dioxid in the laboratory, 
the equations being so arranged as to represent the results when the 
same initial weight of copper sulphate is taken in each case. The 

• The figures in parenthesis throughout this bulletin refer to the bibliography on page •!•'>. 

s Tin- formulae arc expressed id term ol the English Imperial gallon, which weighs 10 pounds, while the 
r. s. gallon weighs 8.3389 pounds, and the English fluid ounce, which is equivalent to 1/20 pint, or 28 cc, 
while the ''. s. fluid ounce la equivalent to 1/lGpint, or 29.6 ec. 



PICKERING SPRAYS. 3 

actual weight of pure lime (calcium oxid) and the approximate 

volume of clear limewater which would contain this lime are also 

given in each case. 

Formula A (4 CuO, S0 3 ). 

Proportions required: Crystallized copper sulphate 1, lime 0.169 
(6:1); or copper sulphate 1 ounce, 1 limewater 134 ounces. 2 

REACTION. 

(A) 10 CuS0 4 + 7.5 CaO = 10 CuO, 2.5 S0 3 +7.5 CaS0 4 
(A')10 CuO, 2.5 SO3+3.75 C0 2 = 3.75 (CuO) 2 , C0 2 +2.5 CuS0 4 

This formula represents a 25 per cent re-formation of copper sul- 
phate. 

Formula B (5 CuO, S0 3 ). 

Proportions required: Crystallized copper sulphate 1, lime 0.18 
(5.56:1); or copper sulphate 1 ounce, 1 limewater 143 ounces. 2 

REACTION. 

(B) 10 CuS0 4 +8 CaO = 10 CuO, 2 S0 3 +8 CaS0 4 
(B')10 CuO, 2 SO3+4 C0 2 = 4 (CuO) 2 , C0 2 +2 CuS0 4 

This formula represents a 20 per cent re-formation of copper 

sulphate. 

Formula C (10 CuO, S0 3 ). 

Proportions required: Copper sulphate 1, lime 0.203 (5:1); or 
copper sulphate 1 ounce, 1 limewater 161 ounces. 2 

REACTION. 

(C) 10 CuS0 4 +9 CaO = 10 CuO, S0 3 +9 CaS0 4 

(C) 10 CuO, SO3+4.5 CaO = 4.5 (CuO) 2 , C0 2 +CuS0 4 

This formula represents a 10 per cent re-formation of copper 

sulphate. 

Formula D (Ordinary Bordeaux Mixture). 

Proportions required: Equal weights of copper sulphate and lime; 
or copper sulphate 1 ounce, 1 limewater 800 ounces. 2 

REACTION. 

(D)10 CuS0 4 +44 CaO = 10 CuO, S0 3 , 3 CaO +9 CaS0 4 +32 CaO 
(D') 10 CuO, S0 3 , 3 CaO +7.5 C0 2 = 

4.5 (CuO) 2 , C0 2 + 3 CaC0 3 + CuSO* 

This formula represents a 10 per cent re-formation of copper 
sulphate. 

1 Avoirdupois. 2 Fluid imperial ounces. 



4 i;i l.l.l.riX B66, V. s. DEPARTMENT OF AGRICULTURE. 

The results of their laboratory tests, in which there-formed copper 
sulphate was determined after carbon dioxid had been passed through 
the various basic sulphates, led Bedford and Pickering to believe that 
the Formula A spray, re-forming 40 percent of the copper sulphate, 

was from 12 to 1". times as effective as ordinary Bordeaux mixture 
(Formula D), which re-formed 2.8 per cent of the copper sulphate, 
and that the Formula C spray, re-forming 22 per cent of the copper 
sulphate, was about 8 times as effective as the standard Bordeaux 
(Formula D). 

These in\ e^tigators (4) stated also that, "the efficacy of a fungicide 
must not be estimated by the amount of copper contained in it, but 
by the amount which becomes soluble and therefore available for 
fungicidal action. Nor should the efficiency of a spray be judged by 
the visible deposit left on the leaves, for even if it were composed 
entirely of copper compounds it does not follow that it would be 
more efficacious than some other deposit which might be invisible. 
In most cases the deposit consists largely of material which is quite 
inefficient and may be detrimental to fungicidal action, as is the lime 
which constitutes four-fifths of the deposit visible after spraying with 
ordinary Bordeaux mixture." Later they reported that the idea 
that the fungicidal action of standard Bordeaux spray does not com- 
mence until several days after its application had been definitely dis- 
proved, and that the effects of the application of Bordeaux do not 
become visible at once because time is necessary for the decay of the 
tissues, which is the case even when a copper salt in solution is 
applied, but that the excess of lime in ordinary Bordeaux causes the 
fungicidal action to proceed more slowly. Pickering, however, be- 
lieved that in ordinary or standard Bordeaux made with milk of 
lime the copper reacts and undergoes on the tree the changes given 
under the reaction for Formula D (p. 3). 

Swingle (23), Sicard (22), Bell and Taber (5), Vermorel and Dan- 
tony (24), and others have discussed the chemical composition of 
standard Bordeaux sprays, which are prepared by mixing a solu- 
tion of copper sulphate with milk of lime. These two ingredients 
are brought together in various ways, and the manner of mixing 
undoubtedly affects the chemical and physical properties of the 
spray. The details of the many theories covering the chemical 
reactions which take place when copper sulphate and calcium 
hydrate are mixed need not be considered here. 

Opposed to the belief held by Pickering and others that the copper 
<f Bordeaux is slowly made active by the carbon dioxid of the air 
are the statements by Lutman (14) that Bordeaux mixture is 
fungicidal immediately upon application. This writer considers that 
the lime particles iii Bordeaux have fungicidal properties. Swingle 
(23), in L896, advanced a series of ideas as to possible methods 



PICKERING SPRAYS. 5 

whereby the copper of Bordeaux prevented fungous infection of 
plants. Gimingham (10) and Barker and Gimingham (1, 2) do not 
accept the theory of Pickering that the carbon dioxid of the air 
renders the copper soluble in Bordeaux, but believe that the per- 
meable cell walls of the spores absorb copper from insoluble copper 
compounds in the spray. 

In 1902 Clark (8) stated that the process of rendering soluble por- 
tions of the copper hydrate (Cu(OH) 2 ) of Bordeaux mixture, which 
under orchard conditions is of fungicidal value, is accomplished 
chiefly by the solvent action of the fungus spores, which have the 
power to dissolve enough, copper to kill themselves. The host plant 
has a certain power of dissolving copper hydrate deposited on its 
leaves. 

PHYSICAL PROPERTIES. 

A spray must so distribute the copper compound it contains as to 
completely cover the trees or plants in a thoroughly uniform manner 
and must possess the proper adhesive properties. If either of these 
physical properties is lacking, the spray fails to accomplish its pur- 
pose. 

Various settling tests with Bordeaux prepared in different ways 
have been made, and numerous adhesives have been tried.' Haw- 
kins (12), who gives a detailed description of such tests, states that 
Pickering sprays remain in suspension better than ordinary Bordeaux. 
Lutman (13), in his data, which include descriptions of the precipita- 
tion membranes formed in freshly prepared Bordeaux, states that 
the slow settling properties and the presence of the precipitation 
membranes in freshly prepared Bordeaux are in a great measure 
responsible for its superiority as a protective agent against fungous 
diseases. This investigator studied the areas covered by 1 cubic 
centimeter of the various sprays tested on glass slides, as a result of 
which he concludes that "very dilute solutions such as Pickerings 
possess a greater covering power for the amount of materials used." 

The physical properties of the Pickering, or limewater Bordeaux, 
sprays are not described by Pickering, but have been studied by 
Lutman (14) and by Butler (6). Butler, who has investigated the 
formation of sphere crystals in various copper sprays, claims that the 
rate at which they form depends on the concentration and tempera- 
ture of the mixture. Both of these investigators state that the film 
membranes of the Pickering sprays do not deteriorate as do those in a 
regular Bordeaux spray, and that the sphere crystals are not formed 
in Pickering sprays, even after long standing. This is an important 
point, as the formation of such crystals signifies a breaking down of 
the precipitation membranes and a deterioration of the spray. 



6 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

GENERAL CONSIDERATIONS. 

Butler (7) slates that freshly prepared Pickering spray has a li<rht- 
blue color, which becomes deep blue on standing. He found a 
neutral or acid Bordeaux, such as the Pickering sprays, to acl more 
quickly than ordinary Bordeaux, and reported that the Pickering 

spray was less injurious to grapes than ordinary Bordeaux. He 
states that the toxic value of the unit copper is the same in acid, 
neutral, and alkaline Bordeaux, hut is more available for immediate 
action in the Pickering than in the ordinary Bordeaux sprays. 

According to McAlpine (15), who compared the results of Pickering 
with those of standard Bordeaux sprays on apple trees, the two 
varieties are equally effective in controlling black spot (Fusicladium 
dendriMcum). The limewater Bordeaux adhered just as well as the 
standard Bordeaux, and had the additional advantages of being free 
from gritty particles, of acting at once on the spores of the fungus, 
and of containing a much smaller percentage of bluestone. The 
check trees gave 92.5 per cent of good fruit, indicating that the 
black spot was not sufficiently severe to give definite results. 

F. de Castella (9) states that Pickering's claims concerning the 
greater efficacy of the limewater sprays are not borne out in practice. 
He reports that after extensive trial they have been found decid- 
edly inferior to 2 per cent Bordeaux and that the use of Pickering 
sprays can not be recommended. He considers the Woburn or 
Pickering paste sold in England to be satisfactory but not superior 
to Bordeaux. The greater solubility of the tetra-cupric sulphate 
seems to be a defect rather than an advantage according to this 
writer, for the reason that, while more active at first, it is removed by 
heavy rains more readily than the ordinary Bordeaux deposit, thus 
rendering the duration of the protection insufficient. No data are 
given by this writer to substantiate his claims. 

PURPOSE OF PRESENT INVESTIGATION. 

If the results obtained by Pickering in the laboratory in England 
hold true under field conditions in America, it is obvious that a great 
saving in copper in this country may he effected. This investigation 
was planned, therefore, for the purpose of outlining a practical 
method of preparing a copper fungicide which would be more effective 
per unit of copper than standard Bordeaux. The experiments were 
conducted with the following primary objects in view: 

(1) To determine whether sprays made in accordance with the 
various Pickering formulas (p. 3) were effective when applied under 
American field condit ions. 

To ascertain how much copper in the form of the different 
Pickering formulas is required per given quantity of spray to insure 
effective control of fungous diseases. 



PICKERING SPRAYS. 7 

(3) To compare the fungicidal values of certain of the more prom- 
ising Pickering sprays with those of standard Bordeaux mixture per 
unit of copper. 

(4) To determine the injurious action of the more promising 
Pickering sprays on various kinds of vegetation as compared with 
that of standard Bordeaux. 

(5) To compare the adherence of Pickering sprays with that of 
standard Bordeaux. 

PREPARATION OF SPRAYS USED. 

Pickering sprays made according to Formulas A and C (p. 3) 
were used in such proportions that the finished sprays prepared hy 
Formula A would contain the equivalent of 0.64, 0.38, 0.13, and 
0.065 per cent of copper sulphate, and those prepared by Formula 
C, 0.36, 0.23, and 0.115 per cent of copper sulphate. In making the 
stock solutions of limewater and copper sulphate these directions, 
outlined by Bedford and Pickering (4), were followed: 

Dissolve the copper sulphate by suspending it in a piece of sacking, near the top 
of the water, in a wooden or earthenware container. Place not less than 2 or 3 pounds 
of some good quicklime (CaO) in a wooden container, slake with a little water, and 
add the desired amount of soft water. After making a smooth paste, add water, stir 
the lime and water two or three times, and let settle. Cover the container. Carbonate 
of lime found on top of the water does no harm. Run off the desired amount of the clear 
limewater, and mix with the required amount of copper sulphate solution. Test to 
be sure that all the copper has been combined with lime, and dilute to the required 
volume with water. To test for free copper, put a few drops of a solution of ferro- 
cyanide of potash in a white saucer with water and drop into this some of the clear 
liquid obtained after the limewater Bordeaux has settled. If a brownish-red color- 
ation appears, it indicates that copper remains in solution, a little more limewater 
must be added, and the solution retested. 

To prepare Pickering (A) 1 sprays containing in the finished product 
the equivalent of — 

0.64 per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
(prepared so that 1 gallon is equivalent to 1 pound of copper sulphate) to obtain 2 
pounds, 10.7 ounces of crystallized copper sulphate with 42.88 U. S. gallons of the 
stock limewater,~and make up the total volume to 50 U. S. gallons. 

0.38 per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
to obtain 1 pound, 9.3 ounces of crystallized copper sulphate with 25.47 U. S. gallons 
of the stock limewater, and make up the total volume to 50 U. S. gallons. 

0.13 per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
to obtain 8.67 ounces of crystallized copper sulphate with 8.71 U. S. gallons of the 
stock limewater, and make up the total volume to 50 U. S. gallons. 

0.065 per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
to obtain 4.33 ounces of crystallized copper sulphate with 4.36 U. S. gallons of the 
stock limewater, and make up the total volume to 50 U. S. gallons. 

1 Throughout this bulletin capital letters in parenthesis following "Pickering" indicate the formula 
used in making the spray. 



8 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

T<> prepare Pickering (C) sprays containing in the finished spray 

the equivalent of — 

>; per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
to obtain I pound, 8 ounces of crystallized cupper sulphate with 38.08 U. 8. gallons 
of the stock limewater, and make up the total volume to 50 V. S. gallons. 

cent copper sulphate: Mix enough of the Btocfe solution of copper sulphate 
to ohtain L5.3 ounces of crystallized copper sulphate with 18.62 U. 8. gallons of the 
stock limewater, and make up the total volume to 50 V. 8. gallons. 

0.1L~> p< r a nt copper sulphate Mix enough of the stock solution of copper sulphate 
toobtain 7.7 ounces of crystallized copper sulphate with 9.26 U. 8. gallons of the stock 
limewater, and make up the total volume to 50 U. S. gallons. 

Samples of water used in the various localities for the preparation 
of Pickering and Bordeaux sprays, analyzed by the Water Laboratory 
of the Bureau of Chemistry, contained very little lime or any other 
constituent that might interfere with the preparation of sprays, 
such as the Pickering sprays, which are made according to definite 
formulas and are said to depend for their activity on the presence of 
definite compounds, the basic sulphates of copper. According to 
the tests of Bedford and Pickering (3, 4), slight variations in the 
amounts of limewater employed result in the formation of different 
basic sulphates of copper, each of which functions as a fungicide in 
a characteristic way. 

In slaking Jime it is important to add just enough water to make 
it heat, after which water is added slowly to keep the lime from 
burning. When the reaction nears completion more water is added 
to make a paste. Finally, when the total amount of water required 
has been added, the solution is stirred to form saturated limewater. 

RESULTS OF INVESTIGATION. 
potatoes. 

Blight Control and Yield, 
pickering and standard bordeaux sprays in 1916. 

Six acres of Green Mountain potatoes in northern Maine (near the 
Aroostook Farm at Presque Isle) were selected for these experiments. 
As the sprayer was made to spray four rows at a time, the field was 
divided into four-row plats which, in turn, were subdivided into 
200-foot lengths. Since the field was S00 feet long, four subdivisions 
were made in each group of four rows. A certain spray was applied 
to the first and third 200-foot plats, another one to the second and 
fourth 200-foot plats, etc. Thus each spray was applied to one plat 
in the front and to one in the rear of the field. The plats were so 
arranged that each four-row plat where any particular spray was 
being tested had a four-row plat of Bordeaux-sprayed potatoes on 
one side and a four-row check plat on the other. 

Seven Pickering sprays were tested. Four (those used on plats 
1, 2, 3, and 4) were made according to Formula A, while three (those 



PICKERING SPRAYS. 9 

used on plats 5, 6, and 7) were made by Formula C. All the Pickering 
sprays were applied with a hand-pump apparatus on July 19 and 
August 2, 10, and 17. Bordeaux was applied on these days, and 
also on July 26. Thus the Pickering sprays were applied four and the 
Bordeaux five times. Headings for blight, both early and late, were 
made by three observers working independently, those for the late blight 
(Phytophihora infestans) being made on the two middle rows of each 
plat. The average figures obtained from two observations by each of 
these individuals are recorded, in terms of the estimated percentage 
of the total foliage infected, in Table 1. The potatoes from the 
several plats were picked up separately and weighed, the yield results 
thus obtained being given in Table 1 . 

Table 1. — Effect of various sprays on blight and yield of potatoes (northern Maine, 1916). 





Spray used. 


Copper 

sulphate 

in spray 

used. 


Early blight. 


Late blight. 


Yield of tubers.' 


Plat No. 


Front of 
field. 


Rear of 
"field. 


Front of 
field. 


Rear of 
field. 


Front of 
field. 


Rear of 
field. 




Bordeaux, 5-5-50 


Percent. 
1.25 
.115 


Per cent. 
52 
67 
66 
64 
59 
63 
68 
65 
50 
61 
67 
64 
56 
63 
59 
72 


Per cent. 
59 
73 
80 
78 
78 
86 
S3 
78 
41 
58 
68 
55 
58 
61 
64 
70 


Per cent. 

7 
40 
60 
43 

5 
53 
53 
13 

7 
36 
54 
27 

4 
21 
21 

5 


Per cent. 
4 
5 
7 
5 
2 
6 
7 
5 
2 
6 

21 
4 
3 
7 

12 
3 


Pounds. 
1,189 

1,165 
1,202 
1,221 
1,225 
1,170 
1,189 
1,1X7 
1,252 
1,283 
1,309 
1,260 
1,276 
1,313 
1,220 
1,179 


Pounds. 
1,026 

957 


6 


(heck 




5 


Pickering (C) 


.23 

1.25 

. 065 


963 

1,027 




Bordeaux, 5-5-50 


4 


Check 






3 




.13 

1.25 

.36 


901 




Bordeaux, 5-5-50 


7 


1 , 260 


Check 




1 




.64 
1.25 

.38 


1,426 




Bordeaux, 5-5-50 


2 








1 190 


2a 


Pickering (A) and rosin- 
fish-oilsoap. 


.3S 


1,016 





1 Determinations were made on 200-foot depth of field, four -row plats. 

The blight in 1916 was not severe. The late blight on the potatoes 
under observation was very irregular, being marked in certain parts 
of the front of the field, particularly on the check plats, while the rear 
showed but little. On August 24 the vines in plat 1 and in those 
sprayed with Bordeaux were green, while those in all the other plats 
had died. 1 The best results for the control of late blight (PJiytopMhora 
infestans) on potatoes were obtained with standard Bordeaux, 5-5-50. 
The average estimated percentage of late blight on all of the plats 
sprayed with Bordeaux was A\, the extremes being 2 and 7. 

The average yield for all of the plats sprayed with standard Bor- 
deaux was 1,205 pounds of tubers, and for the check plats 1,176 
pounds. Plat 1, sprayed with the Pickering (A) spray, containing 
0.64 per cent of copper sulphate, averaged 1,343 pounds of tubers, 
and showed 27 and 4 per cent of blight in the front and rear portions 

1 A portion of this field was sprayed commercially by the owner, starting with a Bordeaux, 4-1-50, and 
finishing with a Bordeaux, 7-7-50 or 8-8-50. Neither the length of life of the vines nor the yield was in- 
creased by this treatment. 

180971°— 20— Bull. 866 2 



10 BULLETIN 806, U. S. DEPARTMENT OF AGRICULTURE, 

of the field, respectively. Plat 2a, receiving the Pickering spray 
which contained 0.38 per cent of copper sulphate and was mixed 
with rosin-fish-nil soap, showed 5 and 3 percent of blight, and a yield of 
1,098 pounds, while plat 'J. receiving the same spray without the soap. 
showed 21 and 7 percent of blight, and a yield of 1,261 pounds. Plat 
3, receiving Pickering spray with an 0.13 per cent copper sulphate 
content, showed 13 and 5 per cent of blight, while plat 7 gave 36 and . 
(i per cent for blight. All the Pickering-sprayed plats were next to 
a check plat, while those receiving the Bordeaux were protected by 
sprayed plats on each side. 

No rotten tubers were found on any of the plats. As is often the 
case, some variation occurred in the yields from different portions of 
the field. The vines of the check plats were not injured by driving 
through the plats, a factor of some importance in view of the fact 
that the spray cart was driven twice through some of the sprayed 
plats and four times through others when each spray was applied. 

It is interesting to note that the average yields of the Pickering- 
sprayed plats just discussed varied with the percentage of copper 
sulphate present in the spray. The increased yield of the sprayed 
vines over that of the unsprayed Vines was small, because cf the dry 
weather and the early date at which the vines died. 

The weak Pickering sprays (containing 0.23 per cent of copper 
sulphate or less) did not give satisfactory blight readings or results 
for yield. While the 0.64, 0.38, and 0.36 per cent copper sulphate 
Pickering sprays gave little indications of controlling the late blight 
in the front plats, they showed some control on the rear plats, and 
all the yields were satisfactory. No differences in the action of the 
Pickering (A) and Pickering (C) sprays were noticed. The copper in 
these sprays did not appear to be 12 times as effective as that in 
the standard Bordeaux sprays, but per unit of copper present the 
Pickering sprays looked promising. It was accordingly decided to 
t iv Pickering sprays containing a higher percentage of copper sulphate 
the following year. 

PICKERING AND BORDEAUX SPRAYS IN 1917. 

The arrangement of the plats adopted in 1916 (p. 8) was varied 
somewhat in 1917, in that the plats were arranged in triplicate and 
the various plats receiving the same treatment were placed in three 
different sections of the field. 

The copper sulphate content of the Pickering sprays tested varied 
from <>.:'. to 6.7 per cent (Table 2). Rosin-nsh-oil soap, 2 pounds to 
:.d gallons, \\:i- added to the Pickering (A) spray applied to plat 12, 
and dry arsenate of lead, 1 pound to 50 gallons, to the Pickering 
(A) spray applied to plat 13 and to the Pickering (C) spray applied 
to plat l t. Bach of these three sprays contained 0.5 per cent of cop- 



PICKERING SPRAYS. 



11 



per sulphate. Green Mountain (Norcross strain) potatoes, grown on 
new land, were sprayed six times during the season, using a Watson 
sprayer, after the vines were 10 or 12 inches above the ground. 

Portions of the two middle rows of each plat were read for blight 
and used for the yield data. The blight readings (Table 2) are the 
averages of the last readings of four individuals who worked inde- 
pendently of one another. The results obtained with Bordeaux spray 
(PL I, fig. 1) are more favorable than those secured from using 
the Pickering spray, with the exception of that applied to plat 1, 
where they were equally as good (PL I, fig. 2). The Pickering 
sprays which contained less than 0.5 per cent of copper sulphate did 
not control the blight as effectively as the standard Bordeaux and 
the Pickering sprays containing 0.6 or 0.7 per cent of copper sulphate. 

Table 2. — Effect of various sprays on blight and yield of potatoes (northern Maine, 1917)} 



Plat No. 



Check 



Check. 



Check. 



Check. 



Check. 



Check. 



Check. 



Check. 



Check. 



Check. 



Check. 



Spray used. 



Pickering (A) 

Bordeaux, 5-5-50. 



Pickering (A) 

Bordeaux, 5-5-50. 



Copper 

sulphate 

in spray 

used. 



Per cent. 
0.7 
1.25 

O.'fi" 

1.25 



Pickering (C) 

Bordeaux, 5-5-50. 



0.6 
1.25 



Pickering (A) 

Bordeaux, 5-5-50. 



0.5 
1.25 



Pickering (C) 

Bordeaux, 5-5-50. 



0.5 
1.25 



Pickering (A) . . 
Bordeaux, 5-5-50. 



0.4 
1.25 



Pickering (C) 

Bordeaux, 5-5-50. 



Pickering (C) 

Bordeaux, 5-5-50. 



Pickering (A) and rosin-fish-oil soap. 
Bordeaux, 5-5-50 



Pickering (A) and lead arsenate. 
Bordeaux, 5-5-50 



Pickering (C) and lead arsenate . 
Bordeaux, 5-5-50 



0.4 
1.25 



0.3 
1.25 



0.5 
1.25 



0.5 
1.25 



0.5 
1.25 



Late 


Yield of 


blight. 


tubers. 


Per cent. 


Pounds. 


44 


406 


45 


■ 384 


57 


347 


52 


409 


41 


414 


85 


321 


48 


404 


42 


415 


95 


335 


53 


3'J2 


42 


393 


88 


301 


53 


349 


43 


325 


84 


296 


67 


355 


37 


415 


96 


309 


76 


381 


39 


399 


96 


320 


63 


337 


41 


451 


96 


270 


56 


345 


41 


366 


96 


294 


56 


406 


42 


430 


96 


270 


57 


358 


44 


396 


96 


294 



Rotten 
tubers. 



Per cent. 
12 
14 
12 
13 
10 
10 
10 
11 
10 
12 
10 
10 
14 

8 
12 
10 
11 

7 
11 

8 

9 
14 
11 

9 
11 
17 
11 
11 
13 

9 
10 
16 
11 



» Determinations were made on two rows, each 300 feet long. 

The total yield results for plats 1, 2, and 3, treated with Pickering 
sprays, and for the corresponding Bordeaux-sprayed and check plats 
are as follows: Pickering, 1,219 pounds; Bordeaux, 1,213 pounds; 
and check, 1,003 pounds. Plats 4 and 5, to which the Pickering 
spray having an 0.5 per cent copper sulphate content was applied, 
yielded 741 pounds of tubers; the corresponding Bordeaux-sprayed 
plats, 718 pounds; and the check plats, 597 pounds. The plats 



12 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

treated with Pickering Bprays containing less than 0.4 per cent of 
copper sulphate yielded less than the corresponding Bordeaux- 
sprayed plats hut more than the check plats. The yield of tubers 
from the sprayed plats showed an increase of from 30 to 40 per 
cent over that from the unsprayed plate. 

A bigh proportion of rotten tubers was found on all the plats. 
This was due principally to the wet weather, but partially to the 
late start made in applying the sprays. The percentage of rotten 
tubers from the various plats is too variable to permit of any definite 
conclusions. The tubers from the check plats showed no more rot 
than those from the sprayed plats. Barrels of potatoes from several 
of the plats treated with Pickering and Bordeaux sprays, as well as 
from the check plats, were stored in a potato cellar until February, 
1918, when the tubers were sorted. The percentage of rot found 
among the potatoes from the various plats was very uniform. 

In 1917 the blight was severe, and the land used for the experi- 
ments was uneven, which gave some of the plats a decided advantage 
over others. The results showed that a Pickering spray containing 
0.7 per cent of copper sulphate is in all respects as ^efficient as a 
Bordeaux, 5-5-50, containing 1.25 per cent -of copper sulphate. 
No differences were noted in the relative efficiency of the Pickering 
(A) and (C) sprays. While these sprays were not shown to be 12 
times as effective as standard Bordeaux, the indications were that 
they were more efficient per unit of copper in the solution used than 
the Bordeaux mixture. 

PICKERING AND BORDEAUX SPRAYS IN 1918. 

Series 1. — Tests with Pickering (A) spray, containing 0.7 per cent 
of copper sulphate, were made on two farms in the vicinity of Presque 
Isle, as well as on the farm used in 1916 and 1917. Each spray was 
applied five t imes to acre plats, usbig a Watson sprayer, tw T o nozzles per 
row, in two instances, and a new single-nozzle sprayer in the other. 
Twice during the season the vines were double sprayed. 

The blight, while widespread in July, and threatening to do as 
much damage as in the previous season, was stopped by the dry 
weather during August. The blight readings on the vines, made by 
t luce individuals working independently, were low, 2 per cent or less, 
for the Pickering- and Bordeaux-sprayed plats. The check plats 
showed from 20 to 50 per cent of blight. Evidently, , then, the 
Pickering sprays applied in 1918 cheoked the blight as effectively 
as did the Bordeaux mixture. 

The yield results on two of the farms varied greatly, according to the 
location of the plats, because of an uneven distribution of manure 
and fertilizer over the fields. On the farm previously used for the 



Bui. 866, U. S. Dept. of Agriculture. 



Plate I. 




Fig. I. 



-Potato Vines Sprayed with Bordeaux, 3-3-50 (Plat 55), and 
Unsprayed (Plat 54). 




Fig. 2. 



-Potato Vines Sprayed with Pickering Spray (Left of Stake 43) and 
Unsprayed Vines (Right of Stake 43). 



Bui. 866, U. S. Dept. of Agriculture. 



Plate II. 




Fig. I. — Potato Vines Sprayed with Bordeaux. 5-5-50 (Plat B), and with 
Pickering Spray (Plat I). 



■ 


|r*js mi m wrntf-' ~ ~ K«iM . h ^ 


^ HI 


> SHI 1 Mffl A -i>j 



Fig. 2. — Potato Vines Sprayed with Barium-Water Spray (Plat 59) and 
Unsprayed (Plat 58). 



PICKERING SPRAYS. 



13 



experimental work, however, where, the treatment of the soil was 
uniform, increased yields were obtained from the plats treated with 
the Pickering and Bordeaux sprays. 

Series 2. — A second series of tests was conducted in northern 
Maine in 1918, using (1) a Bordeaux spray, (2) Pickering (A) and (C) 
sprays, (3) a spray in which the limewater was replaced by barium 
water, and (4) an 0.6 per cent solution of copper sulphate to which 
powdered arsenate of lead (1 pound to 50 gallons) had been added. 
In all cases the sprays were made to contain 0.6 per cent of copper 
sulphate. Green Mountain (Norcross strain) potatoes were first 
sprayed when the vines were 5 or 6 inches above the ground, after 
which they received five applications with a Watson sprayer, using 
two nozzles to a row. The results of this work are recorded in Table 3. 

Table 3. — Effect of various sprays on blight and yield of tubers {northern Maine, 1918). 



Plat No. 



Farm 1. 



Check. 
Farm 2. . . 



Farm 3. 



Farm 1 (2d series): 

1 

2 (cheek) 

3 

4 

5 

6 

7 



9 (check) 2 . 



Spray used. 



Pickering (A) 

Barium water 

Bordeaux, 5-5-50. 
Bordeaux, 4-4-50. 
Bordeaux, 4-2-50. 
Bordeaux, 4-1-50. 



Pickering (A) 

Barium water 

Bordeaux, 5-5-50. 
Bordeaux, 4-4-50. 
Bordeaux, 4-2-50. 
Bordeaux, 4-1-50. 



Pickering (A) 

Barium water 

Bordeaux, 5-5-50. 
Bordeaux, 4-4-50. 
Bordeaux, 4-2-50. 
Bordeaux, 4-1-50. 

Bordeaux, 5-5-50. 



Pickering (A) 

Pickering (C) 

Bordeaux, 24-2^-50 

Barium water 

Copper sulphate and lead arsenate . 
Bordeaux, 5-5-50 



Copper 

sulphate 

in spray 

used. 



Per cent. 
0.7 
.7 
1.25 
1.0 
1.0 
1.0 



.7 

.7 
1.25 
1.0 
1.0 
1.0 

.7 

.7 
1.25 
1.0 
1.0 
1.0 

1.25 



.00 
.00 
.60 
.60 
.60 
1.25 



Late 
blight. 



Per cent. 
2.0 
1.0 
1.7 
1.0 
3.0 
2.7 
20-50 

1.2 
1.6 
1.2 
1.5 
1.7 
1.8 

1.3 
2.3 
2.0 
1.3 
1.9 
2.5 

.5 
33.0 
1.7 
1.3 
3.0 
1.7 
1.8 
1.2 
45.0 



Yield of 
tubers.' 



Pounds. 
274 
277 
247 
276 
258 
277 
215 

2G1 
264 
279 
243 
198 
222 

227 
303 
224 
295 
370 
375 

244 
235 
241 
251 
248 
241 
237 
242 
175 



i Determinations made on two rows, each 150 feet long. 



2 Plat partially shaded. 



The blight readings of all the plats sprayed were practically the 
same (1 to 3 per cent), while the vines on the check plats showed 
33 and 45 per cent infection. The yields were remarkably uniform 
for all the plats, with the exception of the last check plat, which was 
shaded by the adjacent trees. The dry season and the fact that the 
vines were killed by frost on September 9 tended to reduce the 
increased yields which are usually obtained from sprayed plats. 
Here the Pickering sprays containing 0.6 per cent of copper sulphate 



14 



BULLETIN 8G6, U. S. DEPARTMENT OF AGRICULTURE. 



gave as good results as the Bordeaux sprays containing L.25 per cent 
of copper sulphate. In fact, all of the sprays gave practically the 
same results. The only plats giving yields l>elo\v 240 pounds were 
the two check plats and the one treated with copper sulphate and 
lend arsenate. The yield and blight readings were practically the 
same for the plats sprayed with the Pickering solution as for those 
sprayed with Bordeaux mixture (Plate II, fig. 1). 

In Central Maine. — Separate plats of about \ acre each of Green 
Mountain and .Rural New Yorker seed potatoes, in Foxcroft, Me., 
were treated with Pickering and barium-water sprays of 0.7 per cent 
copper sulphate content, and witli reduced lime Bordeaux, 4-4-50, 
4-2-50, and 4-1-50, sprays. The rest of the 8-acre field was sprayed 
with a standard Bordeaux, 5-5-50. Plats sprayed with standard 
Bordeaux were placed between the experimental plats. A spray 
wagon treating six rows at a time was used. As the vines were not 
sprayed until July 15, they were double sprayed at each spraying, or 
four times altogether. The results of these tests are given in Table 4. 

Table 4. — Effect of various sprays on late blight and yield of potatoes (Central Maine, 

1918). 



Plat 
No. 



Spray used. 



Bickering (A) 

Barium water 

Bordeaux, 4-4- .V). 
Bordeaux, 4-2-50. 
Bordeaux, 4-1-50. 
Bordeaux, 5-5-50. 



Copper 
sulphate 
in spray. 



Per cent. 
0.7 
.7 
1.0 
1.0 
1.0 
1.25 



Green Mountain. 



Blight on 
vines. 



Per cent. 
Trace. 

...do 

...do 

...do 

...do 

...do 



Yield, i 



Pounds. 
:m 

322 
285 
338 
381 
258 



Rural New Yorker. 



Blight on 
vines. 



Per cent. 
Trace. 
...do.... 
...do.... 
...do.... 
...do.... 
...do.... 



Yield.' 



Pounds. 
.(24 
332 
285 

333 

319 
330 



1 Obtained from two rows, 150 feet long. 



s A ledge of rock in this plat. 



On the whole, the blight results were uniform and very low. Early 
in August a trace of blight appeared through this and other fields, 
but the dry August practically put an end to it. The yields of Green 
Mountain tubers varied somewhat, particularly at the lower end of 
the field where plats 5 and 6 were located, but plats 1, 2, and 4 gave 
practically the same yields. The Rural New Yorker potatoes were 
grown on a more uniform portion of the field, so that they showed 
uniform results, except in plat 3, where a ledge of rock reduced the 
yield. Only traces of blight were seen on the Rural New Yorker 
vines, which are much more rangy and stand up from the ground 
higher than the Green Mountain vines, making them less liable to 
infections of late blight. 



BARIUM-WATER SPRAYS IN l'HO. 

It was thought that the greater solubility of barium hydrate over 
lime might be an advantage in the preparation of a spray like the 



PICKERING SPRAYS. 15 

Pickering sprays. While barium hydrate costs much more than 
lime, barium, unlike lime, is dissolved, leaving no residue. Barium is 
said to possess some fungicidal powers which lime does not. Oster- 
hout (16) noticed a peculiar contraction of certain species of spyro- 
gyra in 0.0001 molecular solution of barium chlorid, winch was not 
produced by chlorid of lime or other salts. 

A spray containing 0.38 per cent of copper sulphate was prepared 
by dissolving barium hydrate in water and adding the copper sul- 
phate solution to the barium water. When necessary more barium 
water was added until no free copper was present, as determined by 
tests with potassium ferrocyanide. 

In 1916 this spray was applied four times, while the regular 5-5-50 
Bordeaux was applied five times. The plats sprayed with barium 
water were next to the check plats and the Bordeaux-sprayed plats 
were between two sprayed plats. The blight readings were: Barium- 
water-sprayed plats, 25 and 12 per cent; Bordeaux-sprayed plats, 
12 and 10 per cent; check plats, 75 and 41 per cent. The yields of 
tubers were: Barium-water-sprayed plats, 1,142 and 1,052 pounds; 
Bordeaux-spraj^ed plats, 1,125 and 1,168 pounds; check plats, 1,058 
and 1,138 pounds. In view of the fact that only 0.38 per cent of 
copper sulphate was present in the spray and but four applications 
were made, while the Bordeaux was applied five times, these results 
were sufficiently satisfactory to warrant additional tests. 

BARIUM-WATER SPRAYS IN 1917. 

In 1917 a barium-water spray made to contain 0.7 per cent of 
copper sulphate was tested. The average percentage of late blight 
on the vines was: Check plat, 76 per cent; barium-water-sprayed 
plat, 21 per cent; Bordeaux-sprayed plat, 13 per cent. The yield 
of tubers and percentage of rot from the two middle rows of each plat, 
each row being 100 feet long, were: Standard Bordeaux-sprayed 
plat, 148 pounds, 8 per cent rot; barium-water-sprayed plat, 168 
pounds, 5 per cent rot; check plat, 130 pounds, 6 per cent rot. The 
barium-water-sprayed plat adjoined a check plat, wliile the Bor- 
deaux-sprayed plat had sprayed plats oiueither side. 

BARIUM-WATER SPRAYS IN 1918. 

In 1918 a barium-water spray containing 0.7 per cent of copper 
sulphate, which had given excellent results in 1917, was tested on 
acre plats in a commercial way, and another barium-water spray, 
containing 0.6 per cent of copper sulphate, was tested on a smaller 
scale. 

The plats to which 0.7 per cent barium-water spray was applied 
on the commercial scale gave blight yield readings of from 1 to 2.3 
per cent as compared with readings of from 1.2 to 2.0 per cent in the 



1() BULLETIK 866, U. S. DEPARTMENT OF AGRICULTURE. 

case of those sprayed with standard Bordeaux and of from 20 to 50 
per cent in the ease of the unsprayed plats. The barium-w ater- 
sprayed plats yielded from 264 to 303 pounds of tubers, the Bor- 
deaux-sprayed plats from 247 to 313 pounds, and the check plats 
215 pounds. 

The application of the 0.6 per cent barium-sulphate spray to 
smaller plats gave an average blight reading of 1.7 per cent, as com- 
pared with 0.5 and 1.2 per cent for the Bordeaux, 5-5-50, mixture, 
and 33 and 45 per cent when no spray was used. The yields of 
tubers from two rows, each 150 feet long, were: Bordeaux-sprayed 
plat, 2 11 pounds; check plat, 235 pounds; barium-water-sprayed plat, 
2 1 1 pounds. 

These results, extending over three seasons, particularly those of 
1917 and 1918, indicate that a spray made.with barium hydrate and 
containing 0.7 per cent of copper sulphate gives a satisfactory control 
of blight and the same yield of tubers as a Bordeaux, 5-5-50, con- 
taining 1.25 per cent of copper sulphate. Plate II, figure 2, shows 
the protective action given by the barium-water spray in 1918, when 
the blight was severe. 

In preparing the barium-water spray containing 0.7 per cent of 
copper sulphate, equal parts of copper sulphate and barium hydrate 
(2.8 pounds of barium hydrate and 2.8 pounds of copper sulphate to 
50 gallons) were found to be satisfactory. While such a spray gave 
good results and reduced the copper sulphate used 44 per cent, the 
price of barium hydrate is so high that such a spray can not be con- 
sidered commercially practicable at the present time. If the price 
of barium hydrate drops, or if barium chlorid, which sells for $75 per 
ton, can be used, an effective spray may be cheaply prepared. The 
fact that no residue is left, that the barium hydrate may be added to 
the spray tank with the water and dissolved there, and that there is 
reduced wear and tear on apparatus, may induce a trial of this spray, 
particularly if the yields are shown to be stimulated to a greater 
extent than with Bordeaux, 5-5-50. 

REDUCED MILK-OP-LIME SPRAYS IN 1917. 

if 

Bordeaux, 3-3-50 and 3—1^—50, sprays were applied to potatoes 
during the season of 1 i > 1 T. The reason for reducing the proportion 
of lime used as milk of lime was to determine its influence on the 
fungicidal power of the copper and its effect upon the adhesive prop- 
erties of the spray. 

Blight control.— Check plat, 71 per cent; plat sprayed with Bor- 
deaux, 5-5-50, 13 per cent ; plat sprayed with Bordeaux, 3-3-50, 38 
pei- cent ; and plat sprayed with Bordeaux, 3-1 £-50, 26 per cent. 

Y'ald. Check plat, 139 pounds; plat sprayed with Bordeaux, 
5-5-50, L58 pounds: plat sprayed with Bordeaux, 3-3-50, MS 
pounds; plat sprayed with Bordeaux, 3-1^-50, 172 pounds. 



PICKERING SPRAYS. 17 

Rotten tubers. — Check plat, 3 per cent; plat sprayed with Bordeaux, 
5-5-50, 4 per cent; plat sprayed with Bordeaux, 3-3-50, 8 per cent; 
plat sprayed with Bordeaux, 3-1^-50, 8 per cent. 

The Bordeaux, 5-5-50, spray gave the lowest average readings for 
blight. The largest yield of tubers came from the plat sprayed with 
Bordeaux, 3-H-50. Apparently the percentage of rotten tubers was 
not influenced by the spray used. The fact that the plats sprayed 
with Bordeaux, 3-3-50 and 3-1^-50, were on lower ground than the 
other two plats, together with the wetness of the season, accounted 
for the high percentage of rotten tubers found on them. 

REDUCED MILK-OF-LIME SPRAYS IN 1918. 

In 1918 one-acre plats were sprayed with Bordeaux, 4-4-50, 4-2-50, 
and 4-1-50, to determine the influence of varying amounts of lime 
on a definite amount of copper. The average results of these tests, 
which were conducted on the same fields as the Pickering and barium- 
water tests, appear in Table 3. 

The blight readings are so low that it is impossible to draw a definite 
conclusion from them. Those for the plats sprayed with Bordeaux, 
5-5-50 and 4-4-50, are lower than those for the plats sprayed with Bor- 
deaux, 4-2-50 and 4-1-50. While the Bordeaux, 4-1-50, gave some- 
what larger yields than the other sprays, the average yields of tubers 
were practically the same for all the sprayed plats. The slight varia- 
tion which exists is undoubtedly due to the location of the plats and 
the fertilizer used rather than to the sprays. 

Adherence of Copper from Sprays to Leaves. 

The power of various sprays to adhere to potato leaves was tested 
by Girard (11), who employed standard Bordeaux, Bordeaux made 
with half the usual amount of lime, Bordeaux made with aluminum 
sulphate, copper and soda mixture, and copper and acetate of lime 
mixture. The sprayed plats were subjected to artificial rain for vari- 
ous periods. The Bordeaux spray made with half the usual amount 
of lime left the largest amount of copper on the leaves. The addition 
of sulphate of aluminum was of no value. Butler (7) also concludes 
that a Bordeaux mixture made with a medium amount of lime has 
greater adhesive properties than one to which the full amount of lime 
has been added, and considers the alkaline Bordeaux sprays more 
adhesive than the acid or neutral Bordeaux sprays. 

Method of estimating copper on leaves. — To determine how much 
of the copper from the various sprays actually remained on the potato 
leaves, sets of 50 leaves were picked from the vines on the different 
plats, the leaves from each plat being placed in separate envelopes. 
Directly after picking tracings were made of the outlines of the leaves 
and were later measured with a planimeter to obtain the areas of 

180971°— 20— Bull. 866 3 



Is BULLETIN 866, U. S. DEPARTMENT OF .\<;i:i< ri/rri;K. 

the loaves. The area of one side of the leaves only was used in mak- 
ing the calculations. The leaves were dried and used for analysis 
for copper. The results were expressed as milligrams of copper per 
square millimeter of leaf surface. By weighing the leaves when dry 
it was then possible to express the results both as parts of copper per 
million on the dried leaves and us milligrams of copper per square 
meter of leaf surface. 

Method of determining copper on leaves. — The leaves were placed 
in I '.-inch porcelain dishes and ashed in the muffle at dull red heat. 
The ash was covered with 30 cc. of 1-3 nitric acid and allowed to 
stand over [light. It was then filtered and washed, the filtrate made 
faint I v ammoniacal, and brought to a boil. Next it was cooled, 
made (<> suitable volume, and filtered. An adequate aliquot was 
taken for the colorimetric estimation of the copper. This aliquot, as 
well as solutions of standard copper sulphate, containing added am- 
monia and nitric acid, were evaporated to dryness in clean, white, 
3-inch porcelain dishes. To the residues 5 cc. of distilled water and 3 
drops of acetic acid were added, and finally 3 drops of 10 per cent 
potassium ferrocyanid, the dishes being rotated to mix the solutions, 
which were immediately compared with the standards. The results 
are expressed as parts of copper per million. This method has been 
checked against the electrolytic copper method and found to give 
good results. The standard copper sulphate solution was made to 
contain 0.0001 gram of copper per cc. 



On August 12, two days after the third spray had been applied, a 
set of leaves (lot 1) was taken from the vines on the sprayed plats. 
On August 24, seven days after the leaves had been sprayed, addi- 
tional samples of leaves (lot 2) were taken. The results of the analy- 
ses, which were made in duplicate, are given in Table 5. Average 
results for four sets of leaves, or 200 leaves, from each plat show that 
the barium-water and three of the seven Pickering sprays employed 
left a higher percentage of copper on the leaves to 0.1 percent of cop- 
per sulphate present in the spray than Bordeaux, 5-5-50. The other 
four Pickeringspraysdidnotshowas high a ratio of copper on the leaves 
as did the Bordeaux, 5-5-50. It must be remembered, of course, 
that the Pickering sprays were applied four times, while the Bordeaux 
spra\ was applied live times. Although the Bordeaux-sprayed leaves 
always showed the presence of more copper than any of the others, it 
is apparent that, considering the amount of copper sulphate used, the 
copper of the Pickering sprays adhered equally as well. The leaves 
from the vines treated with Pickering (A) spray and rosin-fish-oil 
soap showed the presence of more copper than did those from the 
vines sprayed with plain Pickering (A) spray containing 0.38 per cent 
of copper sulphate. The amounts of copper on the leaves of the vines 



PICKERING SPRAYS. 



19 



sprayed with Pickering (A) and (C) sprays varied markedly. On an 
average more copper was found on the leaves sprayed with Pickering 
(C) sprays than on those treated with Pickering (A) sprays. 

Table 5. — Adherence of copper from various sprays to potato leaves (northern Maine). 





Spray. 


Cop- 
per 
sul- 
phate 

in 
spray. 


Copper adhering to leaves. 


Plat 
No. 


Parts per million 

(dry basis). 


Parts per mil- 
lion per 0.1 
per cent 
CuS0 4 in 
spray (dry 
basis). 


Mg. per 
square meter 
ofleafsurface. 


Mg. per 

square meter 

ofleafsurface 

per 0.1 per 

cent CuS0 4 

in spray. 




Lot l.« 


Lot 2.2 


Lot l.i 


Lot2.« 


Lot l.i 


Lot 2.2 


Lot 1.' 


Lot 2.2 


1916. 


Standard Bordeaux, 
5-5-50 


Per 
cent. 
1.25 
.64 
.38 
.13 
.065 
.23 
.115 
.36 

.38 
.38 

.7 
.6 
.6 
.5 
.5 
.4 
.4 
.3 

.5 

.5 

.5 
1.25 


163.3 
149.7 
29.4 
35.8 
9.11 
42.9 
36.6 
61.8 

120.8 
73.6 

519.8 
455.1 
422.6 
338.1 
277.5 
274.2 
111.9 
138.6 

141.4 

128.9 

213.3 

387.4 


332. 6 
53.7 
22.3 
19.6 
7.2 
23.8 
18.9 
97.9 

54.0 
38.0 

571.7 
533.9 
373.6 
431.5 
334.5 
319.3 
200.5 
163.3 

338.0 

275.0 

390.0 
1,073.7 
41.8 
22.05 
956.19 
1,641.60 
1,098.0 
16.9 
878.3 
1,217.5 
1,703.0 

1,700 
1,100 
1,700 
1,500 
1,200 
2,300 


13.0 
23.4 
7.7 
27.6 
14.0 
18.7 
31.8 
17.2 

31.8 
19.4 

74.2 
75.8 
70.4 
69.6 
55.5 
68.6 
28.0 
46.2 

28.3 

25.8 

42.7 
31.0 


26.6 
8.4 
5.9 
15.1 
11.1 
10.3 
16.4 
27.2 

14.0 
10.0 

81.7 
89.0 
62.3 
86.3 
66.9 
79.8 
50.1 
54.4 

67.6 

55.0 

78.0 
86.0 


31.15 

15.77 
8.00 

11.64 

.80 

7.97 

5.99 

12.80 

24.13 
5.98 

11.17 

10. 64 
10.96 
6.98 
5.34 
6.25 
2.11 
3.32 

2.96 

2.66 

4.38 
7.55 


18.61 
13.07 
10.39 
14.13 
8.96 
9.10 
7.00 
3.97 

9.24 

8.57 

10.02 
30.00 


2.5 
2.4 
2.1 
9.0 
1.2 
3.5 
5.2 
3.6 

6.4 
L6 

1.60 
1.77 
1.83 
1.40 
1.07 
1.56 
.53 
1.11 

.59 

.53 

.88 
.60 






Pickering (A) 






do 

do 

do... 






Pickering (C) 






do 

do 

Pickering (A) and 
rosin-fish-oil soap 

Barium water 




1917. 
1 


Pickering (A) 




2 




2.18 
1 73 


3 


Pickering (C) 


4 






5 


do. 




6 


do 




7 


Pickering (C) 


1 78 


8 






12 

13 
14 

Check. 


Pickering (A) and 
rosin-fish-oil soap 

Pickering (A) and 
lead arsenate 

Pickering (C) and 
lead arsenate 

Bordeaux, 5-5-50 


1.85 

1.71 

2.00 
2.40 


Check. 




















Check. 


Bordeaux, 3-3-50 

Bordeaux, 5-5^50 


.75 

1.25 

.75 


363.0 
566.4 
618.1 


48.4 
45.3 
82.4 


127.5 
131.3 
146.4 


5.87 
22.12 
11.41 


31.71 
48.74 
31.44 


.78 
1.77 
1.52 


4.23 
3.90 
4.19 




Barium water 


.7 
1.25 
1.25 

.7 

.7 
1.0 
1.0. 
1.0 
1.25 

.6 

.6 

.6 

.6 

.6 


271.4 


38.8 

236 
200 
195 
185 
140 
180 
217 
233 
233 
200 

150 


125.5 
97.4 
136.4 

243 
157 
170 
120 

184 


5.86 


21.37 
36.19 
51.57 


.84 


3.05 




Burgundy mixture 

Bordeaux, 5-5-50 

Pickering (A) 


2.89 






4.13 


191S. 
1 


1,650 
1,400 
1,950 
1,850 
1,400 
2,250 
1,300 
1,400 
1,400 
1,200 

900 




2 












3 


Bordeaux, 4-4-50 

Bordeaux, 4-2-50 

Bordeaux, 4-1-50 

Bordeaux, 5-5-50 










4 










5 










6 










A 












C 
















D 
















E ... 
















F 


Copper sulphate and 
lead arsenate 





























i In 1916, picked two days after spraying, and in 1917, eight days after spraying. 
2 In 1916, picked seven days after spraying, and in 1917, two days after spraying. 

IN 1917. 

Leaves picked on August 11, eight days after spraying (lot 1) and 
on August 24, two days after spraying (lot 2), were analyzed with the 
results shown in Table 5, 



20 e.il.l.KTIN 868, r. S. DEPARTMENT OF AGBII Tl/ni;K. 

Lot I. -The copper of the Pickering sprays adhered to the leaves 
in proportionally greater amounts than that of the Bordeaux spray. 

lVr unit of copper sulphate in the spray more copper was deposited 
on the leaves sprayed with the three Pickering sprays which contained 
the highest percentages of copper sulphate than on those sprayed 
with Bordeaux, but less on the Leaves treated with the other Pick- 
ering sprays. The results for copper on the leaves sprayed with 
barium water were low. Of the leaves treated with the 3-3-50 and 
3-1 \— 50 sprays those receiving the 3-1 £-50 spray showed the largest 
deposits. 

Lot 2. — As a rule, more copper adhered to the Leaves sprayed with 
Bordeaux than to those to which any of the other sprays were applied. 
In several instances, however, the results for the Pickering-spray ed 
leaves were equal to those for the Bordeaux-sprayed leaves per unit 
of copper sulphate in the spray. The addition of lead arsenate or 
rosin-fish-oil soap to the Pickering sprays did not increase the amount 
of copper which adhered to the leaves.' More copper adhered to the 
Leaves sprayed with standard Bordeaux than to those sprayed with 
barium water or Burgundy mixture. 

Average results. — More of the copper of the Pickering (A) than of 
the Pickering (C) sprays adhered to the leaves. In three of the eight 
Pickering sprays tested, the copper adhered to the leaves in a higher 
proportion per copper sulphate content of the spray than the copper 
of the standard Bordeaux, 5-5-50. The Bordeaux, 3-H-50, spray 
gave higher results than either the Burgundy mixture or barium water. 
In proportion to the amount of copper sulphate present in the spray, 
the Burgundy mixture gave the lowest results of all. 



During the season of 191S, the adherence of copper to potato leaves 
was determined for Pickering (A) spray, containing 0.7 per cent 
of copper sulphate, for barium-water spray, with the same copper 
sulphate content, and for Bordeaux, 4-4-50, 4-2-50, and 4-1-50, 
sprays, each containing 1 per cent of copper sulphate. The results 
(Table 5) are very uniform except those for the Bordeaux, 4-1-50, 
spray, used on plat 5, which gave lower figures than the sprays used 
on plats 1, 2, 3, 4, and 6. The highest average figure for copper per 
unit of copper sulphate in the spray was obtained in the case of the 
Pickering (A) spray with a copper sulphate content of 0.7 per .cent, 
applied to plat 1. In the tests on plats A, C, D, E, and F, in which 
sprays containing 0.6 per cent of copper sulphate were employed, the 
amount of copper adhering on the leaves treated with Pickering (C) 
Bpray was the same as the amount adhering to those sprayed with 
Bordeaux. The leaves sprayed with Pickering (A) spray gave 
slightly lower results and those treated with the barium-water spray, 



PICKERING SPRAYS. 21 

still lower ones. The solution of copper sulphate and lead arsenate 
did not seem to adhere to the leaves as well as the other sprays. 

SUMMARY. 

The various Pickering and Bordeaux sprays tested adhered equally 
well to the potato leaves. Little difference was noted between the 
adhesive property of the copper from the Pickering (A) and that of 
the copper from the Pickering (C) solutions. The 1916 results favored 
the Pickering (C) spray, while the 1917 results were higher in the case 
of Pickering (A) sprays. The addition of either rosin-fish-oil soap or 
lead arsenate to a Pickering spray failed to increase its adhesive 
properties. In 1916 the results on leaves sprayed with barium-water 
spray were higher than, in 1917 lower than, and in 1918 equal to 
the standard Bordeaux results. A reduction in the amount of milk 
of lime used in preparing a standard Bordeaux type of spray did not 
appear to influence the adhesive properties of the spray until the 
amount used was less than that necessary to combine with the copper 
present, when a decrease in adhesive power resulted. The copper of 
the Burgundy mixture (sal-soda Bordeaux) did not adhere as well as 
the copper of standard Bordeaux, for the reason that all of the copper 
had not been precipitated by the sal soda. 

Injury to Vines and Tubers. 

No injury to vines or tubers was observed as the result of the appli- 
cation of any of the sprays used in these tests. 

Summary, 
pickering sprays. 

A Pickering spray containing 0.7 per cent of copper sulphate con- 
trolled the late blight as well as, and gave yield results equal to those 
obtained with, Bordeaux, 5-5-50, containing 1.25 per cent of copper 
sulphate. The copper in the Pickering sprays was apparently twice 
as effective as that in standard Bordeaux, 5-5-50. Pickering sprays 
containing 0.6 per cent of copper sulphate gave the same yield of 
tubers and nearly as effective control of late blight as Bordeaux, 
5-5-50. Pickering sprays containing less than 0.6 per cent of copper 
sulphate did not give satisfactory control of late blight. The claims 
of Bedford and Pickering (3, 4) that the copper of the limewater 
sprays is from 10 to 12 times as effective as the copper of standard 
Bordeaux were not substantiated by the results of these experi- 
ments. Pickering (A) and (C) sprays were found to be equally 
effective in controlling late blight on potatoes. 

The Pickering sprays adhered to the leaves as well as standard 
Bordeaux. The use of rosin-fish-oil soap or lead arsenate with Pick- 



22 BULLETIN 866, U. S. DKPARTMKXT OF AGRICULTURE. 

ering Bprays did not materially influence their adhesive properties on 

potato leaves. No injury to the leaves or to the potato plants was 
caused by any of the Pickering sprays tested. 

The amount of copper sulphate essential for the control of late 
blighl on potatoes in Maine may he reduced 14 per cent by the use of 
Pickering sprays. The amount of lime required is reduced also and 
all grit removed from the spray, while at the same time the wear and 
tear on spray machinery is greatly diminished. These results were 
obtained in Maine where the principal potato trouble is late blight. 
It is impossible to state what the efficacy of Pickering sprays on 
potatoes would be in sections where other troubles predominate. 

HARIUM-WATER SPRAYS. 

Tests with a barium-water spray containing 0.7 per cent of copper 
sulphate showed that it gave practically the same control of late blight 
and the same yields as Bordeaux, 5-5-50. In fact, in 1917 and 1918 
the yields were slightly larger on plats sprayed with barium water 
than on those sprayed with Bordeaux. 

REDIK ED-MII.K-OF-I.IMK SPRATS. 

The 3-1^-50 spray tried in 1917 (a severe blight year) gave a 
larger yield and a lower blight reading than the 3-3-50 spray. In 
1918, the blight readings for the plats where the 4-1-50 spray w r as 
employed were a little higher than for those where the 4-4-50 spray 
was used. Apparently the amount of lime present in a Bordeaux 
spray used for potatoes in Maine has little effect on the fungicidal 
power. As long as sufficient lime is present to combine with the cop- 
per, the extra lime has no fungicidal advantage, but has several dis- 
advantages. 

Less copper adhered to the leaves when a 4-1-50 spray was em- 
ployed than when 1-4-50 and 4-2-50 sprays were used. This may 
be explained by the presence of free copper sulphate in the 4-1-50 
sprays. 

STANDARD BORDEAUX SPRAYS. 

In sections where the blight may be severe, such as northern 
Maine, a Bordeaux, 5-5-50, is recommended. In other States where 
the blight is usually less severe a Bordeaux, 4-4-50, is desirable. 

GRAPES. 

Control of Fungous Diseases, 
in new jersey. 

Four acres of Concord grapes near Vineland, N. J., were treated 
with Bickering (A) and (C) sprays, varying in copper sulphate con- 
tent from 0.005 to 0.04 per cent, and with a standard Bordeaux, 



PICKERING SPRAYS. 



23 



3-3-50, spray, containing 0.75 per cent of copper sulphate. A 
Pickering (A) spray containing 0.38 per cent of copper sulphate was 
used alone and in combination with rosin-fish-oil soap. One plat 
was held unsprayed as a check plat. The sprays were applied on 
May 18, May 27, June 15, and July 7, 1916. A power sprayer was 
used for each spraying with the Bordeaux and for the May sprayings 
with the Pickering spray, while a hand-pump sprayer was employed 
for the June and July applications of the Pickering spray. Because 
of injury to the vines sprayed with the strongest Pickering solutions 
after a severe hail storm occurring on June 11, no further applica- 
tions of these sprays were made. The spraying of one or two rows of 
grapes with the weaker Pickering sprays was, however, continued 
throughout the season. 

Table 6. — Effect of various sprays on blight and yield of grapes {New Jersey). 





Spray used. 


Cop- 
per 
sul- 
phate 

in 
spray. 


Condition of fruit when 
picked. 


Net 
weight 

of 
grapes 
picked 
from 
two 
rows. 




Plat 
No. 


Sound. 


Black 
rot. 


Downy 
mil- 
dew. 


Total 
dis- 
eased. 


Spray injury noted June 13. 


1 

2 

2 

3 

3 

4 


do 

Pickering (A) and 
rosin-fish-oil soap. 

Pickering (A)« 

do.3 

do 


Per ct. 
0.64 

.38 

.38 

.13 
.13 
.065 

.23 

.23 

.115 

.36 

. 75 


Per ct. 
0) 

(') 

(') 

76.12 

71.68 

69.63 

(') 

C) 

85. 09 

(') 

92.91 
.00 


Per ct. 
(') 

0) 

(') 

21.17 

25.00 

25.98 

(') 

(') 
12.43 

(') 

6.79 
70. 64 


Per ct. 

0) 

(') 

(>) 

2.71 
3.33 
4.39 
(') 

(») 

1.48 

(') 

.29 
37.53 


Per ct. 

(') 

(') 

0) 

23.88 

28.33 

30.37 

(') 

C 1 ) 

14.01 
(') 

7.02 
100.(1(1 


Lbs. 
121 

411 

784 

961 
1, 501 

949 

1,502 

892 

1.375 
830 


Leaves and fruit greatly 
injured; many buds de- 
stroyed. 

Almost complete defolia- 
tion: part of fruit de- 
stroyed. 
Do. 

Leaves noticeablv injured. 

Do. 
Leaves slightly injured. 
Large proportion of leaves 
destroyed. 

Do. 


5 

5 


do3 


6 


do 


Leaves slightly injured. 
Large proportion of leaves 

destroyed. 
Leaves slightly injured. 


7 


do 


Check.. 


Bordeaux, 3-3-50 











1 Fungus control satisfactory. 
8 Spray applied three times. 



3 Spray applied to first two rows four t imes. 



The results for the control of fungous diseases in New Jersey 
(Table 6) indicate that the control of disease was in direct proportion 
to the spray injury of the vines. Apparently the strongest Picker- 
ing spray, which contained 0.64 per cent of copper sulphate (plat 1), 
controlled the fungous diseases more effectively than the Bordeaux 
sprays, showing the high availability of the copper of the Pickering 
sprays. The injury, however, was so severe that the spray could 
not be used commercially. 



IN VIRGINIA. 



Two acres of grapes, largely Concords, in poor condition, in Vienna, 
Va., were sprayed with Pickering sprays and with a standard Bor- 



24 



BULLETIN B86, U. S. DEPARTMENT OF AdlMCin/rURE. 



deaux, 3 3 50, spray. The Pickering spray was used alone and in 
combination with rosin-fish-oil soap. The sprays were applied four 
times, May 15-16, May 25-26, June 12-13, and July 1-3. L916, with 
a barrel pump sprayer. 

Early in July many spots of black rot were seen on the leaves of 
the check plat, but none on the Leaves of the sprayed plats. On 
June 26 some black-rot spots were observed on the leaves from all 
plats except those sprayed with Bordeaux, 3-3-50, and Pickering 
(A) containing 0.64 per cent of copper sulphate (plats A and 1). 
Plat 7, sprayed with Pickering (C) containing 0.36 per cent of copper 
sulphate, showed very few spots. The check plat showed the largest 
number of infected leaves. One row of vines in plat 1 did not re- 
ceive the second application. These vines showed neither the spray 
injury nor the control of rot apparent in the rest of the vines of 
plat 1. 

Table 7. — Effect of various sprays on black rot of grape leaves ( Virginia). 



Plat No. 


Spray used. 


Copper 
sulphate 
in spray. 


Amount 
of black- 
rot leaf 
spot. 


Remarks. 


A 


Bordeaux, 3-3-50 


Per cent. 

0.75 

.64 

.38 

.38 

.13 
.23 
.36 
.00 


Pet a Hi. 
3.5 
3.5 
5.0 

5.0 

11.0 

6.5 

5.0 

100.0 


Condition of vines good: slightly injured. 


1. . 


Leaves and fniit badly injured. 


2. 


do 


Leaves severely injured; fruit somewhat. 


2b 


Pickering! A landrosin- 
fish-oil soap. 


Do. 


3. . 


Slight burning of leaves. 
Do. 


5.. 




7. 


.do 




Check 




Vines not much injured. 









The results in Table 7 show that the four strongest Pickering sprays 
tested (plats 1, 2, 2b. and 7) and the standard Bordeaux spray gave 
an excellent control of black-rot leaf spot on the leaves. The sprays 
used on plats 3 and 5 gave a less effective control of the disease. 
Black-rot spots were seen on the leaves of all the vines on the check 
plat. The weeds in the vineyard were high, and the weather was 
moist, rendering conditions for infection excellent. Of all the ex- 
perimental plats. No. 5 looked the best, although not as well as the 
plat sprayed with standard Bordeaux. 

Yield. 



IN NEW JERSEY. 



The yield of grapes sprayed varied with the injury to the vines, 
which in turn depended upon the percentage of copper sulphate in 
the Pickering sprays employed. The two weakest (those used on 
plats 1 and 6) gave good yield results, but plat 4 showed only 69 
and plat 6 only 85 per cent of sound berries, as compared with 93 
per cent obtained from the plat sprayed with Bordeaux, 3-3-50. 



PICKERING SPRAYS. 



25 



IN VIRGINIA. 



It was considered impracticable to attempt to determine the 
weight of grapes from the different plats in Virginia. From the three 
rows sprayed with Bordeaux 26 crates of grapes were obtained, an 
average of 8| crates per row. From the 20 rows of grapevines sprayed 
with the Pickering sprays 26 crates of salable grapes were secured, 
an average of 1.3 crates per row. No grapes were harvested from 
the unsprayed check rows. Not all of the grapes from the plats 
sprayed with Pickering spray were picked, as some of the fruit was 
small and immature. 

Adherence of Copper From Various Sprays to Leaves, 
in new jersey. 

Duplicate samples of leaves from the plats treated with the various 
sprays were gathered on June 6 (10 days after the second spraying) 
and on June 8 (12 days after the second spraying). Forty leaves 
from each set were analyzed, the results obtained on those gathered 
on June 6 being shown in Table 8. The area of one side only of the 
leaves was considered in calculating the area figures. The outlines 
of the fresh leaves were traced on paper, and the tracings later meas- 
ured by a polar planimeter (p. 17). 

Table 8. — Adherence of copper from various sprays to grape leaves. 





Spray used. 


Copper 

sulphate 

in spray 

used. 


Copper adhering to leaves. 


Plat No. 


Parts 

per 
million 

(dry 
basis). 


Parts. 

per 
million, 

per 0.1 
per cent 

CuSO< 
in spray. 


Mg. per 
square 
meter 
of leaf 
surface. 


Mg. per 
square 
meter 
of leaf 
surface 
per 0.1 
per cent 
CuS0 4 
in spray. 


New Jersey: 
B... 


Bordeaux, 3-3-50 


Per cent. 
0.75 
.64 
.38 
.38 
.13 
.065 
.23 
.115 
.36 


1,459 
982 
750 
709 
383 
110 
110 
184 
285 
11 

1,440 
191 
18 

392 

174 
321 


194 
153 
197 
187 
295 
170 

48 
160 

80 


64.0 
46.2 
?9.9 
27.8 
14.1 

.4 
4.2 
6.2 
10.5 

.4 

44.6 

6.9 

.7 

16.1 


S.5 


1 




7.2 


2... 


do 


7.8 


?a 


Pickering (A ) and rosin-fish-oil soap. 


7.3 


3 


10.8 


4 


do 


.6 


5 


Pickering (C) 


1.8 


6 


do 


5.4 


7 


...do 


3.0 


Check... 






Virginia: 
A.. . 


Bordeaux 3-3-50 


0.75 

.64 
.38 
.38 
.13 
.23 
.36 


192 

30 

5 

103 


6.0 


1. . 




1.1 


2. 


do 


.2 


2b 


Pickering (A) and rosin-fish-oil soap. 


4.2 


3 




5 . 


Pickering (C) 


76 
89 


5.6 
12.8 


2.4 


7 


do 


3.G 


Check 





















1 Trace. 



The area results show more decisively than do the weight results 
that the copper from the Pickering (A) sprays adhered to the leaves 
in proportionately greater amounts than did that from the Pickering 



26 BULLETIN 866, D. S. DEPARTMENT OF AGRICULTURE. 

( iprays. The leaves sprayed with Bordeaux mixture contained 
more copper and a higher ratio of copper per unit of copper sulphate 

present in the spray than the average for those treated with the 

Pickering sprays, showing that the copper of the Pickering sprays 

djd not adhere to the grape Leaves as well as that of the standard 

Bordeaux spray. The addition of rosin-fish-oil soap to the Pickering 

(A) spray used on plat 2 did not increase the adherence of copper 

to the Leaves. 

IN VIKCINIA. 

Duplicate sets of leaves from the plats treated with the different 

sprays were gathered on June 1 (six days after the second Bpraying) 

and on June 3 (eight days after the second spraying) and analyzed 

(Table 8). 

The results, both by weight and area, for the Leaves gathered dune 1 
-■how that the copper of flic Bordeaux spray adhered practically 
twice as well as that from the Pickering sprays. The use of rosin- 
fish-oil soap seemed to he of decided advantage. These results do 
not agree with those obtained by analyzing leaves in New Jersey 
where similar sprays were used. The low results for copper on 
the Pickering-sprayed Leaves in Virginia, as compared with those 
obtained on Leaves treated with sprays of the same formula and 
strength in New. Jersey, may be accounted for in part by the fact 
that in New Jersey the first two applications were made with a 

power sprayer. 

Injury to Vines. 

in new jersey. 

Until the severe hail storm of dune 11 no burning or other injury 
was noticed on the Pickering-sprayed plats. After the storm, how- 
ever, the leaves were torn, the grapes wen 1 punctured, and young shoots 
broken from the vines. The Pickering-sprayed plats were then re- 
duced in size, only one or two rows of the vines treated with the weaker 
Pickering sprays being continued through the rest of the season. 
The stronger Pickering sprays were dropped entirely. By duly 7 
new foliage had appeared on all the vines and no additional injury 
Was evident . 

Copper sprays used on grapes are often mixed with lead arsenate. 
Lead arsenate, however, was not used with the Pickering or Bordeaux 
sprays in this investigation. Consequently its influence on the 
burning of the foliage was not determined. 

The Pickering sprays containing ().'_>:> per cent and more of copper 
sulphate controlled the fungous diseases as well as the Bordeaux 

spray. As commercial sprays, however, they are impracticable 

because of their tendency to injure the grape leaves and fruit. The 
use of roHn-fish-oil soap with Pickering (A) containing 0.38 per 
cent of copper did not affect the caustic properties of the spray. 



PICKERING SPRAYS. 



27 



IN VIRGINIA. 



On June 10 a heavy hail storm broke the leaves, punctured the 
grapes, and broke off many shoots from the vines. Two or three days 
after the storm serious burning of the leaves was noticed. This in- 
jury was particularly severe on the plats sprayed with the strongest 
Pickering solutions. The weakest Pickering spray produced about 
the same injury as the Bordeaux spray. On June 26 new growth 
appeared on all the sprayed vines, and a fourth spraying was made 
on July 3, with no additional spray injury. As in the case of the 
tests in New Jersey, the injury to the leaves was in direct proportion 
to the percentage of copper sulphate present in the Pickering sprays. 

Among the numerous theories advanced to explain the burning 
or scorching of foliage by copper sprays are the following: (DA 
specific susceptibility of the protoplasm of the plant to copper;. 
(2) solvent properties or activities of the cell sap of the plant on the 
copper compound of the spray; (3) permeability of the epidermis or 
cuticle to the cell contents when conditions are favorable for exos- 
mosis and for a trace of copper which has been rendered soluble; 
(4) weather conditions following spraying, particularly moisture, 
which provides suitable conditions for the exosmosis of some of the 
contents of the cells of leaves; (5) the amount of spray on the leaves 
or foliage, the proportions of other constituents, such as lime, to the 
copper in the spray, the condition of the leaves, whether normal or 
injured by the weather, insects, etc., and, above all, the climate. 

Effect on Maturing of Fruit. 

in virginia. 

At the time of picking, samples of grapes from the different plats 
were analyzed for reducing sugar, sucrose, and acidity, using the 
methods of the Association of Official Agricultural Chemists, in 
order to determine the influence of the sprays in preventing a proper 
maturing of the fruit. 

Table 9. — Effect of various sprays on composition of grapes ( Virginia). 



Plat. No. 



A., 
l.. 
2.. 
2b. 
3.. 
5.. 
7.. 



Spray used. 



Bordeaux, 3-3-50 

l'ickering (A) 

do 

Pickering (A) and rosin-fish-oil s 

Pickering (A) 

Pickering (C) 

.....do.. 



Copper 

sulphate 

in spray 

used. 



Per cent. 
0.75 
.64 
.38 
.38 
.13 
.23 
.36 



Composition of grapes at 
picking time. 



Reducing 
sugar 



Per cent. 
7.35 
10.52 
8.57 
8.54 
7.50 
9.10 
7.60 



Sucrose. 



Pir cm/. 
0.07 
.22 
.42 
.10 
.10 
.28 
.20 



Aridity. 



Cc. nor- 
mal al- 
kali per 
kilo. 
162 
152 
159 
157 
155 
152 
151 



28 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

The results (Table 9) naturally raided with the condition of the 
individual samples. The grapes from plat A, sprayed with standard 
Bordeaux mixture, showed the highest acidity and the lowest sugaf 
content, while those from plat 1, treated with Pickering spray con- 
taining 0.64 per cent of copper sulphate, gave the highest content 
of sugar and a low acidity. Since the percentage of sugar increases 
ami the percentage of acidity decreases during the ripening of grapes, 
no influence of the sprays in preventing a proper maturing of the 
fruit is indicated. On the contrary, an increase in the sugar con- 
tent and a decrease of acid is evident in the Pickering-sprayed grapes, 
compared with those sprayed with Bordeaux. As no unsprayed 
grapes were analyzed, it is impossible to state whether or not the 
copper in the sprays exerted a stimulating action on the grapes. 

The variation in the composition of the grapes sprayed with Pick- 
ering and Bordeaux may possibly he due to the greater availability 
of tiie copper in the Pickering sprays. The fact that more burning 
resulted from using the Pickering sprays than from using the 
Bordeaux sprays is evidence of a greater availability, or at least 
solubility, of the copper of the Pickering sprays. It has been sug- 
gested that the effect of the sprays on the composition of the fruit 
came through foliage injury. 

Summary. 

Pickering (A) and (C) sprays, containing 0.04, 0.36, and 0.38 per 
cent of copper sulphate, caused severe injury to the grape foliage 
and fruit after a hail storm which tore the leaves and injured the 
vines both at Yineland, N. J., and Vienna, Va., in 1916. Under simi- 
lar conditions the Pickering sprays containing 0.23, 0.13, 0.115, and 
0.06.") per cent of copper sulphate caused less injury than the stronger 
Pickering sprays, but more injury than standard Bordeaux. 3-3-50, 
containing 0.75 per cent of copper sulphate. 

The strongest Pickering spray, that employed on plat 1, controlled 
the black rot fully as well as the Bordeaux, 3-3-50, and the Picker- 
ing sprays containing 0.36 and 0.38 per cent of copper sulphate 

showed practically as effective control as the Bordeaux. The weaker 
Pickering sprays, containing 0.23 per cent of copper sulphate or less, 
did not control the black rot as well as the Bordeaux spray. 

The yield of grapes was reduced by all of the Pickering sprays 
except t he two weaker ones. 

The copper of the Pickering sprays did not adhere to the grape 
leaves ;is well as the copper of the Bordeaux, 3-3-50. The averages 
of all the results obtained, including some not reported in the tables, 
show that where the Pickering sprays were applied with a power 



PICKERING SPEAYS. 29 

sprayer as a fine mist (Vincland, N. J.) about one-half as much cop- 
per in proportion to that used in the spray adhered to the leaves as 
when standard Bordeaux was used. When the Pickering sprays 
were applied with a hand pump (Vienna, Va.), the ratio of copper 
retained on the leaves was still further reduced in the case of the 
Pickering sprays. 

The use of rosin-fish-oil soap with one of the Pickering sprays 
proved advantageous in the Virginia tests, but not in the New Jersey 
tests. 

Apparently the copper of the Pickering sprays exists in a more 
active and available form than the copper of the Bordeaux spray, as 
evidenced by the severe burning of the grape leaves. No differences 
were detected in the caustic action or in the adhesive properties of 
the Pickering (A) and (C) sprays. The caustic action and the fungi- 
cidal properties of the sprays made by the two formulas were 
apparently the same. 

The Pickering sprays seem to be too caustic for spraying grapes. 
These sprays, however, may have a very definite use for the last 
application when this must be made late in the season after the 
berries are half grown. Bordeaux spray applied late in the season 
tends to remain on the berries, which is undesirable. Pickering 
sprays, however, are nonstaining. 

APPLES. 

Control op Fungous Diseases. 

An orchard of Yellow Newtown (Albemarle Pippin) trees at Green- 
wood, Va., where bitter rot is prevalent, was selected for these 
experiments. The orchard was not well cultivated and was famous 

as a place for bitter rot. 

in 1916. 

Of the 27 trees in the orchard 12 were sprayed with Pickering 
sprays, 12 with standard Bordeaux, 4-5-50, and three were left un- 
sprayed. The sprays were applied three times, June 23, July 13, and 
July 27. The Bordeaux spray was applied with a power sprayer 
each time. The Pickering sprays were applied the first time with a 
hand-pump sprayer and afterwards with a power sprayer. The 
results of this work are shown in Table 10. 



30 BULLETIN 866, V. S. DEPARTMENT OF AGRICULTURE* 

Tabu 10.— Effect of various spray* on bitter mi of applet | Virginia). 



l'lat No. 


Tree 
No. 


Spray used. 


Copper 
sulphate 
in pray. 


Tola! 
apples. 


Total 

apples 

witli rot. 


A pples 
with rot . 


Dropped 
apples. 


Ipples 

injured 

by 


Defolia- 
tion. 


1916. 


1 
2 
8 

l 

2 
3 
1 
2 
3 
1 
2 


Pickering (A) 

,j<> 


I'll CI III. 

0.13 
.13 
.13 
.066 
.066 
.065 
.33 
.23 
.23 
.116 
.115 
.116 


2, 622 
2,724 
2, 543 
2,934 
2, 576 
1 , 852 
1,820 
91 
2,068 
1,312 
1,7'.)7 
1,961 
3,184 
3,277 
1,196 

3,37:. 

1,628 

2,036 


2. 06 

2,701 

2, 627 

2,918 

2,574 
1,846 
1,810 

86 


l'ir it nl. 
99 
99 
09 

100 

100 

PHI 
UK) 
95 


Percent. 


Pa cent. 


Percent. 












do 










do 








4 


do 










<|o 








5 


Pickering (C) 

do 








5 










do 


2,000 97 

1,297 99 
1,794 100 
1,961 100 








g 


do 








6 


do . 










a 


do . 










i 

2 
8 

1 
2 
3 




3,144 

3,266 
1,196 
2, 566 

1,200 
1,885 


99 
100 

UK) 

76 

74 
93 

f .6 
\ - 2 
J -3 
\ 1-2 
J 4.1 
\ -9 
J -3 
\ - 2 

.5 
15.2 

.1 

.5 
10.3 

.6 

3.5 








Do 












Do 














Bordeaux, 4-5-50 — 
do 


1.00 
l.OO 
1.00 

.50 
.25 
.13 

.50 

.25 
.13 
.50 
.50 


















do .. 








1917. 


Pickering (A) 

do 


3.0 
5.2 
3.0 
6. 3 
10.0 
10.0 
12.7 


96.2 


50 


A. 








82. 3 


50 


A, 




do.'. 






95. 7 


50 
60 
30 


15, 




do 






93.6 


B| 








45.5 
35.7 
12.3 

ti.O 
10.5 

5.5 


98.0 


18 






do 






20 






Bordeaux, 2-2-50 

Bordeaux, 2-1-50 






25.0 
98.0 


16 










20 


(.'heck. . 














Bordeaux, 4-4-50 

Pickering (C) 

Barium water 


1.0 

.58 
.60 






55.8 


20 


1918. 




5,724 
2,594 
:;, 736 
4,552 


200 
50 
736 








2.0 

17.0 
.0 








Check. 














Bordeaux, 4-4-50 


1.00 





















Bitter rot was first seen in this orchard on July 10. On July \'A, 
the time of the second spray application, there was a little bitter rot 
on two of the Bordeaux-sprayed trees and on one check tree. A 
small unhealthy tree in plat 5 showed the most bitter rot. On July 
26, at the time of the third spraying, the following observations 
were made: 

Plat S. — All trees showed a little bitter rot. 

J'/ut .' t . — All trees showed a little bitter rot. 

rial 5. One tree showed a little bitter rot, .and the other two trees 
a good deal of rot. 

I'/nt 6. One tree showed rot at the top, while the other two were 
practically free from pot. 

Bordeaux-8prayed plat. Some trees showed no rot and others 
<|infc a Little. On an average, the trees did not show as much rot as 
the cheek trees. 

('ht<k /'In!. A good deal of rot was seen, more than on the other 
lives in the orchard. 



PICKERING SPRAYS. 31 

As only two barrels of sound apples were obtained from the 27 trees, 
it is apparent that none of the sprays controlled the bitter rot in 1916. 
Although the apples from the trees sprayed with Bordeaux did not 
show as much rot as those from the trees sprayed with Pickering 
sprays or from the check trees, practically every apple from the 12 
Bordeaux-sprayed trees was affected to some extent with bitter rot. 
The failure of any of the sprays to control the bitter rot may be 
explained by the fact that the rot was severe that season, as well as 
by the fact that no spray was applied to the trees after July 27. 

IN 1917. 

Three trees from each of three plats were treated with Pickering (A) 
and (C) sprays, containing 0.50, 0.25, and 6.13 per cent of copper 
sulphate. Bordeaux, 4-4-50, was employed as the standard spray. 
Two trees were sprayed with Bordeaux, 2-2-50, and two with Bor- 
deaux, 2-1-50, sprays, in order to determine the effect of decreasing 
the lime on the fungicidal action of the copper. Several uhsprayed 
trees were left as controls. The sprays were applied with a power 
sprayer four times, June 4, June 22, July 9, and August 2. On August 
2, because of injury caused by the sprays, the spray was applied to 
but one tree of plats A 1} A 2 , A 3 , B 1; B 2 , B 3 , and to but one of those 
sprayed with Bordeaux, 2-1-50. On August 30, counts were made 
of all dropped fruit. All fruit on the trees was picked between Sep- 
tember 14 and 18, and counted for rot and for a late type of Bordeaux 
injury or russeting which developed between August 30 and Sep- 
tember 13. The results are shown in Table 10. 

Scarcely any bitter rot was present in the orchard in 1917. Con- 
sequently, the results prove very little concerning the relative fungi- 
cidal value of the sprays tested. On plat B 3 , the tree sprayed with 
Pickering solution was the only one of the sprayed trees which showed 
any amount of rot, the other two trees of that plat being practically 
free from rot. 

IN 1918. 

Pickering (C) spray and a barium-water spray, similar to the one 
used on potatoes with excellent results (page 11), were used on Cheese 
apple trees. Ten gallons of the barium-water spray were prepared 
by dissolving 8 ounces of barium hydrate in 9 gallons of water and 
adding 2 quarts of copper sulphate stock solution (1 pound per 
gallon), diluting to 10 gallons with water, and stirring thoroughly. 
The Pickering (C) spray was prepared according to the directions 
given on page 7. A Bordeaux, 4-4-50, spray was the standard 
spray. Two trees were sprayed with the Pickering spray, two with 
the barium-water spray, and two with standard Bordeaux, while 
one tree was left unsprayed. The sprays were applied with a power 
sprayer on June 14, June 28, July 26, and August 13. 



32 



BULLETIN B86, U. S. DEPARTMENT OF AGRICULTURE, 



At the time of the third spraying it was noticed that three or four 
apples od the check tree were infected with bitter rot, whereas the 
sprayed trees seemed to he entirely free from it. On August 13, 
the date of the fourth application, one or two apples on the Pickering- 
sprayed, barium-water-sprayed, and Bordeaux-sprayed trees were 
infected with bitter rot, while the check tree showed a fairly large 
amount of rot. 

At the time of picking yen- little bitter rot was found on any of 
the trees. The Bordeaux spray gave 100 per cent protection from 
hitter rot. The barinm-water spray gave a better control of bitter 
rot than the Pickering spray. The 1918 results (Table 10) are incon- 
clusive because of the small number of apples infected with bitter 
rot on the sprayed trees. 

Adherence of C'oppkr from Various Sprays to Leaves. 
IN 1916. 

One set of leaves was gathered from the sprayed and check trees 
on July 12, 13 days after the second spraying, and a second set on 
.Inly L3, three hours after the third spray had been applied. The 
• nit lines of these leaves were immediately traced on paper, and later 
measured with a polar planimeter. The area of each set of 50 leaves 
was calculated, but one side of the leaves being used in the calcula- 
tion. Later the leaves w r ere dried, and the copper determined in each 
set (Table 11). 

Table 11. Adherence of copper from various sprays t<> apple lanes ( Virginia). 



Plat No. 



1916. 



8 

I 

6 

Check. 



1917. 



Check . 



it. 

A 2 . 

A,. 



Spray used. 



Bordeaux, 1-6-60 

Pickering (A) 

....do 

Pickering (C) 

do 

Bordeaux, I 

Pickering ( V) 



Pickering (C) 

... do 



Bordeaux, 4-4-50. 



Bordeaux, 2 1-60. 
Bordeaux, 3 2 60. 

Pickering (A) 

....do 

....do 



Copper 

sulphate 

in spray 

used. 



Pir cent. 
1.00 
.13 
.065 
.23 
.115 
1.00 
.13 
.065 
.23 
.115 



1.00 



.5 
.5 
.50 
. 26 
. 1 26 



Time 
between 
spraying 

and 
gathering 
of leaves. 



Days. 
13 
13 
13 
13 
13 



Copper adhering to leaves. 



Parts per 

million 

(dry 

basis). 



425 
59 
90 

948 

77 
3,150 
260 
186 
646 
219 



316 
255 
206 

148 

62 



Parts per 
million 
per 0.1 
per cent 
ofCuSOi 
in spray. 



42.5 
45.4 
138.5 
in?, s 
67.0 
315. 
200.0 
284.6 
280.9 
216. 6 



64.4 



63.2 
51.0 
41.2 
68. I 
49.6 



Mr. per 
square 
meter of 

leaf 
surface. 



26.0 

1.3 

9.3 

26. 6 

2. 2 

266.6 

16. o 

10.2 

15. 9 

20.3 



33.8 
.8 
16.5 
12.5 
10. 6 
6.5 
3.0 



Mg. per 
square 
meter of 

leaf 
surface 

per 0.1 

per cent 

CuSO< 

in spray. 



2.6 
1.0 

14.3 
11.1 

1.9 
26.7 
12. 8 
15.7 

6.9 
17.7 



3.4 



2.6 
2.4 



PICKERING SPRAYS. 33 

Table 11. — Adherence of copper from various sprays to apple leaves ( Virginia) — Contd. 





Spray used. 


Copper 

sulphate 

in spray 

used. 


Time 
between 
spraying 

and 
gathering 
of leaves. 


Copper adhering to leaves. 


Plat No. 


Parts per 

million 

(dry 

basis). 


Parts per 
million 
per 0.1 
per cent 
of C11SO4 
in spray. 


Mg. per 
square 
meter of 

leaf 
surface. 


Mg. per 
square 
meter of 

leaf 
surface 
per 0.1 
per cent 
CuSC-4 
in spray. 


1917. 
Bi 




Per cent. 

0.50 

.25 

.125 

1.00 


Days. 
15 
15 
15 
25 
25 
25 
25 
25 
25 
25 
25 
25 
25 






28 
28 
28 
28 


362 

136 
52 
955.9 
3.2 
374.8 
595.2 
800.9 
445.8 
126.0 
683.3 
390.0 
172.3 

2,250 
3,250 
4,350 
6 
1,450 
2,400 
4,150 
20 


72.4 
54.4 
41.6 
95.6 


16.5 

7.5 

3.0 

46.8 

0.15 

21.1 

32.3 

37.4 

22.2 

5.6 

33.6 

19.3 

9.4 


3.3 


B 2 


do 


3.0 


B 3 ... 


do 


2.4 




Bordeaux, 4-4-50 


4.7 


Check 






Bordeaux, 2-1-50 

Bordeaux, 2-2-50 


.5 

.5 

.50 

.'25 

.125 

.50 

.25 

.125 

.5S 

.60 

1.00 


75.0 
119.0 
160.2 
178.0 
101.0 
136.7 
156.0 
138.0 

390 
542 
435 


4.2 




6.5 


Ai 


7.5 


A 2 ... 


do 


8.9 


A 3 ... 


do 


4.5 


B, . 




6.7 


B : ... 


do 


7.7 


B 3 ... 


do 


7.5 


1918. 
A... . 






B... 








c 








Check . . . 






A.. 




.58 

.60 

1.00 


250 
400 
415 






B . 








c 


Bordeaux, 4-4-50 






Check . . 








n 









The figures for the copper found on the leaves picked July 26 (13 
days after spraying) show that the leaves sprayed with standard Bor- 
deaux held the most actual copper. Calculated per 0.1 per cent of 
copper sulphate present in the sprays used, however, the leaves 
sprayed with the Pickering sprays held twice as much copper when 
calculated by weight and three times as much when calculated by 
area as did the leaves sprayed with Bordeaux. The figures for the 
copper found on the leaves picked on July 27 (three hours after the 
third spraying) are highest in the case of Bordeaux-sprayed trees. 
The results are much higher for the Bordeaux- than for the Pickering- 
sprayed leaves when expressed by area and slightly higher when 
expressed by weight. Evidently, in proportion to the copper sulphate 
content, the Bordeaux sprays adhered better to the leaves directly 
after application, although the copper of the Pickering sprays ad- 
hered to the leaves in a higher ratio than Bordeaux for the 13-day 
period tested. 

• IN 1917. 

Two sets of 50 leaves were collected in duplicate from the trees 
receiving the different sprays, the first on July 7, two weeks after 
the second spraying, and the second on August 3, nearly four weeks 
after spraying. The leaves were analyzed for copper, the results of 
which appear in Table 11. 



34 BULLETIN 866, D. S. DEPARTMENT OF AGRICULTURE] 

Of the Leaves picked two weeks after spraying, those receiving the 
Bordeaux, l l 50, held the most copper. The leaves sprayed with 
Bordeaux, 2 l 50, held more copper than those on which 2 2-50 
spray was used. No important differences were noted between the 
adhesive properties of the copper of the Pickering (A) and (C) sprays. 

In three cases the leaves treated with the Pickering sprays held prac- 
tically the same amount of copper per 0.1 per cent of copper sul- 
phate used as the leaves sprayed with Bordeaux, 4-4-50. The other 
three Pickering sprays gave lower results. The results for copper on 
the leaves by area were slightly in favor of the Bordeaux spray. 

The analyses of the second set of leaves, gathered nearly four 
weeks after spraying, showed the most copper on the Bordeaux- 
sprayed leaves, although the leaves from plat A, sprayed with 
Pickering spray held 800 parts of copper per million. Contrary to 
the results recorded on page 19, the leaves receiving the Bordeaux, 
2 I 50, spray did not hold as much copper as those sprayed with 
the Bordeaux, 2-2-50. 

All of the Pickering-sprayed leaves held more copper than the 
Bordeaux-sprayed leaves per unit of copper sulphate in the spray 
applied, indicating that per unit of copper sulphate present in the 
spray the copper of the Pickering sprays adheres to apple leaves in 
larger proportions than the copper of standard Bordeaux spray. 

IN 1918. 

Leave- from the trees sprayed with Pickering, barium water, and 
Bordeaux and from the check tree were collected on dune 28, just 
after spraying, and duly 20, 1918, 28 days after spraying, and analyzed 
for copper. The results appear in Table 11. 

As the period from the time of the collection of the first set of 
leaves until the collection of the second set was very dry. about as 
much copper was found on the second Bet as on the first set of leaves. 
The results for the leaves picked immediately after spraying, per 
0.1 per cent of copper sulphate present in the sprays, are highest for 
those receiving the barium-water spray. The Bordeaux-sprayed 
and the Pickering-sprayed leaves gave practically the same results. 
The results for the leaves picked 28 days after spraying from Picker- 
ing-sprayed trees are low, while those for the barium-water- and the 
Bordeaux-sprayed leaves are practically identical. 

In.uhv to Leaves am> Fruit. 



Although the season was wet and sultry, only a trace of injury to 
the Leaves and fruit was noted on the trees treated with Pickering 
spray. This injury had no practical significance. The Bordeaux 
spraj did not injure the leaves or fruit. 



PICKERING SPRAYS. 35 



On June 20 a severe hail storm injured the leaves. On June 21, 
at the time of the second spray application, some burning of the 
leaves on the trees treated with the Pickering sprays was noted, as 
well as a slight burning of the leaves on thq, trees sprayed with Bor- 
deaux, 4-4-50, 2-2-50, and 2-1-50. The burning caused by the 
Pickering sprays was far more noticeable than that due to the Bor- 
deaux sprays, and varied among the trees of the same plat. Little 
difference was evident between the Pickering (A) and (C) sprays 
with respect to caustic properties on this date. On August 2 the 
leaves of the trees on plats A 1; A 2 , and B l showed the most injury. 
Those sprayed with Bordeaux, 2-1-50, also showed severe burning 
of the leaves. The trees in the upper portion of the orchard which 
had been sprayed with standard Bordeaux spray showed marked 
burning of the leaves, while those sprayed with th'e standard Bordeaux 
in the lower part of the orchard showed but slight burning of the 
leaves. 

Part of the Pickering-sprayed trees received only three applica- 
tions, while the others were sprayed four times. The fourth applica- 
tion of the Pickering sprays produced no additional injury. 

All the Pickering sprays reduced the yield of fruit, because of the 
defoliation occurring during July and August. The fruit on the 18 
trees receiving the Pickering sprays was under size. The yield was 
reduced to a greater extent on the trees sprayed with the Pickering 
(A) sprays than on those sprayed with the Pickering (C) sprays. 
Defoliation also caused a reduction in the yields of the Bordeaux- - 
sprayed trees and of those sprayed with Bordeaux, 2-2-50 and 
2-1-50. Pickering (C) sprays produced about the same percentage 
of defoliation as the Bordeaux sprays, while Pickering (A) sprays 
caused much more defoliation. The figures in Table 10 do not show 
any influence of the sprays on the percentage of apples that dropped 
from the trees, which was very high on plats B 2 and B 3 . The A series 
of sprays, which injured the leaves severely and caused the greatest 
amount of spray injury, showed a low percentage of drops. The 
number of drops (10 per cent) from the check trees and the lack of 
increase of drops from the trees treated with the Pickering sprays 
used on plats A x and B x , the two strongest of each formula with respect 
to percentage of copper sulphate, over those from the check trees 
lead to the conclusion that the high percentage of drops for the 
sprayed trees on plats B 2 and B 3 was not due to the sprays used. 

Spray or late Bordeaux injury of apples.— Early in September a 
specking of the fruit on all the sprayed trees was noticed. This 
injury, known as spray or late Bordeaux injury, consisted of red 
spotting usually surrounding a lenticel, and generally found on the 
exposed side of the apple. On some apples the injury was so severe 



36 BULLETIN 866, 0. 5. DBPABTMEVT OP aGRICUI/TUBE 

as to cover the entire exposed cheek with a deep red blush, due to 
the coalescence of individual spots. This type of injury was com- 
mon in this locality, particularly in those orchards which had been 
thoroughly sprayed with Bordeaux. It was most severe on the 
trees which had received the Pickering (A) spray, a little less 
severe on the trees treated with Pickering (C) spray, and very 
apparent on the Bordeaux-sprayed trees. The spotting or late 
Bordeaux injury, shown on all the sprayed trees, reduced the value 
of the 1917 crop. The unsprayed trees yielded the best fruit. The 
reduction of yield due to bitter rot was practically negligible. 

IN 1918. 

At the time of the third spraying, July 26, possibly 5 per cent of 
the leaves on the trees treated with the barium-water spray and some 
on the Pickering-sprayed trees and on the Bordeaux-sprayed trees 
showed a yellowing. The dry weather and heat during the previous 
four weeks may have been responsible for this yellowing which was 
not serious in any case. No injury to the apples was observed. At 
the time of picking no foliage injury of any consequence was observed 
on any of the plats. A brief outline of the theories advanced to 
explain the injury to foliage which frequently results from the applica- 
tion of copper sprays is given on page 27. 

No results to show whether the sprays increased or decreased the 
yield are obtainable. The only available figures on yield are the 
records of the number of apples secured in connection with the 
bitter-rot counts, which are from but one tree of each plat. 

Summary. 

Tn l')l(') practically all of the fruit from the trees treated with Pick- 
ering and Bordeaux sprays and from the check trees was infected 
with hitter rot, which made it impossible to determine the relative 
efficacy of the Pickering sprays. Slight injury to the leaves and 
fruit on the Pickering-sprayed trees was noticed. 

In I'll 7, Pickering (A) sprays containing 0.12, 0.25, and 0.5 per 
cent of copper sulphate injured apple leaves, and caused late Bor- 
deaux injury to the fruit. Pickering (C) sprays of the same strengths 
produced less injury. Standard Bordeaux. 4 4 ."><), spray, containing 
1 per cent of copper sulphate, also injured the leaves and russeted 
the fruit, although not as severely as the Pickering (C) spray. Bui 
little hitter rot was found on any of the Pickering- or Bordeaux- 
sprayed or check trees. Hence no control test of the sprays was 
obtained. 

In L918 no injury to the leaves or fruit, resulted from the use of a 

Pickering (C) spray containing 0.58 per cent of copper sulphate, 



PICKERING SPRAYS. 37 

from a barium- water spray containing 0.6 per cent of copper sulphate, 
or from standard Bordeaux, 4-4-50. The amount of bitter rot on 
the sprayed trees was so small that no definite control results were 
obtained. 

The data on the control of bitter rot by Pickering (A) and (C) 
sprays are rather limited, notwithstanding the fact that the experi- 
ments extended over three seasons. However, 0.5 per cent of copper 
sulphate present in either Pickering (A) or (C) spray gave indica- 
tions of satisfactory control of fungous diseases. 

The Pickering (A) spray is too caustic for use on the apple. While 
less caustic than Pickering (A) sprays, the Pickering (C) sprays 
seem to be more caustic than standard Bordeaux. It is apparent 
that these sprays are more caustic than standard Bordeaux, and can 
not be used on the apple. 

The barium-water spray was tested but one season on the apple. 
While the results were satisfactory with respect to the absence of 
injury, so little bitter rot was present on any of the trees that season 
that no definite control results were obtained. 

Additional experiments are necessary to determine whether a 
Pickering spray containing more limewater than is required in For- 
mula C and the barium-water spray may be safely and efficiently 
used as a fungicide on the apple. 

cranberries. 

Control of Fungous Diseases. 

IN 1917. 

Two Pickering (A) sprays and two Pickering (C) sprays were 
tested on Centennial cranberries in 1917 at Hanover Farms, N. J. 
The percentage of copper sulphate in the four sprays varied from 
0.32 to 0.62. In addition, Bordeaux, 2|-lJ-50, 2^-2^-50, and 
4-3-50, sprays were used. The first two Bordeaux sprays were 
taken for the purpose of comparing the different amounts of lime in 
a Bordeaux spray with the amount in a Pickering spray of the same 
copper sulphate content (0.64 per cent). 

The sprays were applied to small plats, 132 feet long and 8\ feet 
wide, with a hand-pump sprayer, four times during the season, June 14 
(three or four days before full bloom), June 27 (10 days after full 
bloom), July 13, and July 30. Rosin-fish-oil soap, at the rate of 2 
pounds to 50 gallons, was mixed with all the sprays. The berries w 3re 
picked September 15 and sorted for rot soon afterwards. 



38 BULLETIN B86, U. S. DEPARTMENT OF AGRICULTVKi;. 

Tauli: L2. — Effect of various sprays on rot and yield nf cranberries {New Jersey). 1 



!'l:il No 


Spray used. 


Copper 

sul- 
phate in 

spray 
used. 


Total yield. 


Yield per aero 
(calculated). 


All 
berries. 


Rotten berries. 


Ml 
berries. 


Sound 
berries. 


1917. 

I 


PlckeringfA) 


Perct 
J2 

. 10 

.54 
.62 
1.00 
M 
.64 


1 •mi nds. 
67 

661 

531 

60] 

19H 
19J 

54J 

68] 

41 ] 
80i 

HI7! 

38 
74J 

.V.I! 

m 


Pounds. 

H 
ft 

6i 
5 

61 
13 

20] 
30] 

26] 
12 

54 

N 


l'lTd. 

i B 

5.6 
4.4 
G 1 
12 H 
4.2 
2.8 

11.9 
7.3 
15.1 

Hi. 1 

19.1 
20.8 

69 ; 
10.2 

9.7 

12.8 


Bushel*. 


Bushels. 

so 








66 




do 














Bordeaux, 4-8-60 








Bordeaux, U-M-60 








Bordeaux, 2j 2] SO 












\ 


Pickering ( A ) 


.6 
LOO 

1.00 
1.00 




15. 


Bordeaux, i-3-5<.> 






L018. 

1 


Bal soda and roain-fish-oil soap, 4-6- 
60. 

Sal soda and fish-oil emulsion, 4-5- 
50. 


138) 

171} 

207J 
201} 

190 
186] 

148] 

161] 


120] 


2 


158] 


3 (check) .. 


176} 
168} 


1 


Barium waterand rosin-fish-oil soap. 

Pickering (C) and rosin-fish-oil soap. 
Pickering (A; and rosin-fish-oil soap. 


.6 

.6 
.6 




216} 
184] 


6 




57] 


v 


Hordeaux, 4-3-50, and rosin-fish-oil 

soap. 
Bordeaux, 1-2-50, and rosin-fish-oil 

soap. 
Bordeaux, t-1-80, and rosin-fish-oil 

soap. 


1.00 
1.00 
1.00 




B 


134} 


10 


140] 







1 All the cranberries tested were of the Centennial variety, except those on plats A and 13, which were 
Early lilack. 

The percentage of rot found on the berries from all of the sprayed 
plate (Table 12) "was so small that it was impossible to differentiate 
between the sprays with respect to their fungicidal value The 
check plat showed but 12 per cent of rot. The Bordeaux, 2J-1J— 50, 
spray gave the best results for control of rot, but all of the other 
sprays were almost as good. On the large plats (A and B) 4.2 per 
cent of rot was found for berries treated with the spray resembling 
a Pickering spray and 2.8 per cent for those treated with Bordeaux. 
While the data favor the standard Bordeaux spray, the figures arc 
-mall. 

Two large plats (A and B) of Early Blacks were sprayed with a 
power sprayer, one receiving Bordeaux, 4-3-50, the regular spray 
used <»n cranberries at Hanover Farms, and the other a spray resem- 
bling a Pickering spray of 0.6 per cent copper sulphate content, made 
by dissolving in water an amount of lime paste calculated from titra- 
tion- t«. be sufficient to combine with the copper sulphate used. The 
results thus obtained are not comparable with those obtained from 
plats 1 to 8 (Table 12). 

iv 1918. 

Ten small plats of ( "entennial berries at Hanover Farms, X. J., weie 
sprayed with a barrel-pump sprayer on June 11 (three or four days 



PICKERING SPRAYS. 39 

before full bloom), June 25 (10 days after full bloom), July 24, and 
August 12. The small plats were separated by four-foot paths over 
which the spray apparatus was drawn, thus protecting the berries 
on the sprayed .plats from injury like that received in 1917. The 
vines on plats 5 and 6 were heavier than those on the other plats. 
Pickering (A) and (C) sprays, a barium-water spray, two sal-soda 
(NaXOa) sprays, and three sprays of the Bordeaux type, made with 1 
per cent of copper sulphate and varying amounts of lime, were em- 
ployed (Table 12). The sal-soda (Na.,C0 3 ) and fish-oil-emulsion 
spray was prepared by shaking together 1 ounce of water and an 
equal amount of fish oil until emulsified, and then stirring it into the 
spray. The barium-water spray was prepared by the use of barium 
hydrate in place of lime (p. 16). The Pickering (C) spray was made 
with an excess of limewater, and the Pickering (A) spray with just 
the amount of limewater required to neutralize all the copper sul- 
phate present (p. 3). 

As shown by the figures for rotten berries, 15.1 and 69.7 per cent 
for the check plats (Nos. 3 and 7), the amount of rot varied greatly. 
The lowest percentage of rotten berries was obtained on plat 2, 
where sal-soda and fish-oil-emulsion spray was used. 

The following notes were taken on September 5 : 

Plat. 1. — The sal-soda spray resembles the Bordeaux, 4-3-50, spray 
used on plat 8. 

Plat 2. — The berries look sound. More spray is seen on berries 
than on those in plat 1. It occurs in isolated spots or freckles 
rather than in a continuous layer, as is the case with the spray on 
plat 1. 

Plat 3. — Berries are quite sound. Not over 5 per cent of rot is 
visible. 

Plat 4- — Spray is seen distinctly over entire plat. It is the only 
plat that looks blue at a distance. Good protection is afforded, 
although there is more rot than on plats 1 and 2. The spray shows 
regularly on the berries, but is not of uniform density. The berries 
with spray have a festooned appearance, as if each drop of spray on 
drying was thickest at the periphery. 

Pint 5. — But few rotten berries seen. Spray shows plainly in 
spots. 

Plat 6. — Same as plat 5. 

Plat 7. — Estimated 50 per cent rot. 

Plat 8. — Berries very sound. A little more spray visible than on 
either plat 5 or 6. 

Plat 9. — Generally like plat 8. Spray somewhat more apparent. 
Vines not quite as thick as on most of the other plats. 

Plat 10. — Spray shows about like that on plat 9. The northern 
end of the plat is poor land and shows more rot. Rest of plat is very 
sound. 



40 U II. U.TIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

More Bpray was observed on the plat treated with Bordeaux, 

I :; 50, than on those sprayed with the Pickering sprays. It is 
difficull to explain the results obtained with the barium-water spray, 

which, judging from the figures for rot control, produced no effect. 
'Phis spray gave an excellent control of fungous diseases on potatoes, 
as compared with a Bordeaux, 5-5-50. Pickering (A) and (C) 
sprays on plats 5 and 6, where the vines were very dense, showed 
practically identical fungicidal power. The sprays used on plats 
s. 9, and 10 showed good control of rot. From a comparison of results 
with sprays used on plats 8, 0, and 10, it is impossible to determine 
the influence of the different amounts of lime on the fungicidal prop- 
erties of the 1 per cent copper sulphate present in the three sprays. 

Included in the 191S tests were three commercially-sprayed plats, 
treated with a Pickering (0) spray containing 0.6 per cent of copper 
sulphate, a Bordeaux spray made with 0.6 per cent copper sulphate, 
and a Bordeaux, 4-3-50, containing 1 per cent copper sulphate, such 
as is regularly employed for spraying cranberries at Hanover Farms. 
Two bundled gallons of each spray were made and applied with the 
power spray apparatus to Early Blacks. Rosin-fish-oil soap was 
used with all three sprays. The sprays were applied three times, 
June L3, July :i, and July 24. Very little rot was seen on any of the 
plats, and at the time of picking no differences in control of rot on 
the three plats were evident. J\0 check plat was employed. 

Yield. 

IN 1917. 

The calculation of the results for yield of the Centennial berries 
(Table 12) was complicated by injury to the berries due to drawing 
the Bpray apparatus over the vines four times. The high figure for 
yield on the check plat is in part explained by the fact that none of 
the berries on this plat were crushed by the spray cart. Unavoid- 
able irregularities occur in the yields of all plats of cranberries 
of any size. The yield results on Early Blacks are so close that no 
conclusions can be drawn as to the influence of the sprays on the yields 
of berries. 

IN 1918. . 

No results which show t ho influence of the sprays on the yields of 
cranberries are available. 

Adherence of Copper from Various Sprays to Leaves. 

IN 1917. 

Samples of cranberry Leaves were gathered on July 10, two weeks 
after the third Bpray had been applied, and on September 4, five weeks 
after the fourth spraying, and analyzed (Table 13). 



PICKERING SPRAYS. 41 

Table 13. — Adherence of copper from various sprays to cranberry leaves (New Jersey). 



Plat No. 



Spray used. 



Copper sul- 
phate in 
spray used. 



Time be- 
tween 
spraying 
and gath- 
ering. 



Amount of copper. 



Parts per 

million 

(dry basis) 



Parts per 
million per 
0.1 percent 
of copper 
sulphate 
in spray. 



8 (check). 

1 

2 

3 

4 

5 

6 



Pickering 
Pickering 
do... 
Pickering 
Bordeaux 
Bordeaux 
Bordeaux 



(A). 
(C). 



(A) 

,4-3-50.... 
2^-1 }-50. 
2i-2i-50.. 



Per cent. 

0.32 
.405 
.54 
.64 

1.00 
.64 
.64 



Days. 



Picktring 
Pickering 
do... 
Pickering 
Bordeaux 
Bordeaux 

7 | Bordeaux 

8 (check) 



(A). 
(C). 



(A) 

,4-3-50... 
, 2HI-50. 
, 2*-2i-50. 



1918. 



Sal soda and rosin-fish-oil soap . 
Sal soda and fish-oil emulsion . . 

4 Barium water and soap 

Pickering (C) and soap. 



7 (check). 
8 



7 (check). 



Pickering (A) and soap . 



Bordeaux, 4-3-50, and soap 

Bordeaux, 4-2-50, and soap 

Bordeaux, 4-1-50, and soap 

Sal soda and rosin-fish -oil soap . 
Sal soda and fish-oil emulsion . . 

Barium water and soap 

Pickering (C) and soap 

Pickering (A) and soap 



Bordeaux, 4-3-50, and soap . 
Bordeaux, 4-2-50, and soap . 
Bordeaux, 4-1-50, and soap. 



.32 
.405 
.54 
.64 
1.00 
.64 
.64 



110.8 
140.2 
167.2 
166.2 
6S0.2 
407.8 
385.4 
32.6 
80.0 
100.7 
146.7 
131.3 
429.0 
138. 
323.4 



1.0 

1.0 

.6 

.6 

.6 



1.0 
1.0 
1.0 
1.0 
1.0 
.6 
.6 



1.0 
1.0 
1.0 



1,200 

1,300 

1,100 

1,100 

1,400 

47 

1,600 

1,800 

1,600 

330 

3*0 

210 

630 

370 

17 

S40 

1,000 

860 



35 
35 
31 
20 
68 
64 
60 



120 

130 

183.3 

183.3 

233.3 



160 
180 
160 
33 
38 
35 
105 
61. 



84 
100 
86 



The leaves sprayed with Bordeaux held a higher percentage of 
copper than those sprayed with the Pickering sprays, indicating that 
the extra lime of the Bordeaux spray, at least where rosin-fish-oil 
soap was used, is an important factor in increasing the adhesive 
properties of the spray on cranberry leaves. Possibly the copper of 
the Pickering sprays was more efficient as a fungicide per unit of cop- 
per present in the sprays than that of the standard Bordeaux spray, 
although the copper of the Pickering sprays did not adhere to the 
leaves as well as that of the Bordeaux sprays. The results for control 
of rot favor this view. The percentage of rotten berries (Table 12) 
does not speak particularly well for the sprays used on Plats 5 and 7, 
in spite of the fact that the leaves receiving these sprays retained 
the largest amounts of copper (Table 13). The results given in 
Table 13 show nothing concerning the distribution of the copper on 
the leaves or the form and efficacy of the copper on the leaves. 



IN 1918. 



One set of sprayed cranberry leaves was gathered for analysis for 
copper on June 25, directly after the sprays had been applied, and a 



42 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

second Be1 on July 24, four weeks after the last sprays had been 
applied (Table L3). 

The aioel actual copper was found on tin* Leaves sprayed with 
Bordeaux containing 1 percent of copper sulphate (plats 8, 9, and 
10). Calculated per 0.1 per cent of copper sulphate presenl in the 
sprays, the leaves from plats I, 5, and 6, sprayed with the two Pick- 
ering spravs and the barium-water spray, and gathered directly 
after the sprays had been applied, gave the highest results. Of the 
leaves gathered four weeks after spraying, those treated with the Bor- 
deaux spravs (plats 8, 9, and 10) and with the Pickering sprays 
plats .") and 6) gave the highest proportional results. The barium- 
water spray and the two sprays made with sal soda did not adhere to 
the leaves for the four-week period as well as the sprays made with 
lime. The percentage of rotten berries found on the two plats 
sprayed with the sal-soda sprays was low, in spite of the relatively 
small amounts of copper adhering to the leaves at the time of analy>i>. 
Apparently, therefore, the amount of copper adhering to a leaf is not 
necessarily a criterion of its protection from fungous diseases. 

Injury to Leaves and Fruit. 

No caustic action of any of the sprays was noted in either 1917 or 

1918. 

Summary. 

None of the sprays tested injured the leaves or berries. 

The Pickering (A) and (C) sprays were equally effective in control- 
ling fungous diseases. Pickering (A) and (C) sprays prepared with 
0.6 per cent of copper sulphate seemed to give as effective control 
of fungous diseases on cranberries as Bordeaux, 4-3-50, containing 
1 per cent of copper sulphate, although this was not definitely proven. 

Practically the same percentage of copper was presenl on the 
cranberry leaves treated with Pickering spray as on those sprayed 
with standard Bordeaux, rosin-fish-oil soap being used with all the 
sprays. 

Additional tests with the Pickering, barium-water, and sal-soda 
sprays are necessary to obtain conclusive results. 

SUGGESTIONS FOR THE PREPARATION OF PICKERING SPRAY ON A 

COMMERCIAL SCALE. 

The following procedure is recommended for the preparation on 
a commercial scale of a Pickering (A) spray containing 0.7 per cent 
of copper sulphate: 

STOCK sol. I HON OF COPPER SILPHATE (BLUESTONE OR BLUE VITRIOL). 

Suspend 50 pounds of commercial crystalline copper sulphate 
in a gunny sack in 20 or .">() gallons of water in a clean barrel over 



PICKERING SPRAYS. 



43 



night, placing the copper sulphate just beneath the surface of the 
water. This may be conveniently done the evening before the spray 
is to be applied. Remove the gunny sack, stir the solution of copper 
sulphate with a wooden paddle, make to 50 gallons with water, and 
stir again. Keep the barrel or container covered. The barrel or 
container must not leak. The solution thus prepared contains 1 
pound of copper sulphate per gallon. Smaller amounts of the copper 
sulphate may be dissolved, using the same proportions of copper 
sulphate and water 

SATURATED LIMEWATER. 

Place 2 pounds of unslaked lime of a good grade in a clean barrel 
or other wooden container, sprinkle with a little water, and let stand. 
In a few minutes, when the lime crumbles,' add 2 or 3 quarts of water. 
Stir the lime and water until a smooth paste is formed, adding a 
little more water if needed. Finally, fill the barrel and stir six or 
eight times, allowing the insoluble particles of the lime to settle after 




/ATS/OE **?£ J Off *t 

TH/CKA/esses 

OF 
CHEESECLOTH 



Fig. 1.— Apparatus Tor filtering limewater. 

each stirring. Then cover and let stand until used. The limewater 
may be drawn from the barrel by means of a faucet placed 3 or 4 
inches from the bottom. The limewater should be passed through 
a strainer (fig. 1) before it is allowed to flow into the mixing tank. 
If preferred, the clear limewater may be siphoned off from the top 
of the barrel directly into the mixing tank. 

In making limewater for spraying on a commercial scale, several 
pounds of lime may be slaked in a large tank, water added, and the 
mixture stirred by means of a mechanical stirrer for 5 or 10 minutes. 
The clear limewater may be drawn from the top of the tank almost 
immediately by arranging a float with attached hose. If from 15 
to 20 minutes are allowed for the lime particles to settle, the clear 
limewater may be drawn from a spigot placed 6 or 8 inches from the 
bottom of the tank. If desired, slaked lime may be placed in bar- 
rels, allowing about 4 pounds of paste to a barrel, water added, and 
the mixture in each barrel stirred six or eight times in turn. The 
suspended particles will settle in about 10 minutes, when the clear 



44 BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 

Limewater may be drawn off" by suction through a hose into the 
mixing tank or barrel. 

In m airing saturated limewater, 2 pounds of unslaked lime, or 4 
pounds of lime paste, to 50 gallons of water are sufficient. 

MIXING. 

Add 23.1 quarts of t lie standard copper sulphate solution (1 pound 
U) B gallon) to a 100-gallon tank containing 93.78 gallons of clear 
saturated limewater, and stir for 1 minute. Lead arsenate or cal- 
cium arsenate may then be added if desired, and 0.42 gallon of water 
to make the volume to 100 gallons. 

The method of preparing limewater is the principal distinction 
between making the Pickering and the standard Bordeaux sprays. 

In the experience of the writer, the Pickering sprays are readily 
prepared, in much less time than many of the proprietary pastes 
which dissolve with difficulty, and take but little more time than 
the standard Bordeaux sprays require. 

SUMMARY. 

Experiments covering three seasons were conducted with Pickering 
(A) and (0) sprays, made to contain from 0.06 to 0.70 per cent of 
copper sulphate. Theemcacyof these sprays was compared with that 
of standard Bordeaux mixtures containing from 0.7."> to 1 .25 per cent of 
copper sulphate. The investigation was carried out under American 
field conditions, in regions where certain fungous diseases are most 
severe. 

The strongest Pickering sprays, those containing from 0.6 to 0.7 
per cent of copper sulphate, controlled fungous diseases on potatoes 
and cranberries very effectively. Their control of fungous diseases 
on grapes and apples was not definitely determined, the results 
being complicated by burning or other injury to the foliage and 
fruit. Pickering sprays containing less than 0.6 per cent of copper 
sulphate were not effective as fungicides for potatoes and probably 
nol t'u- cranberries. No difference between the efficacy of the 
Pickering (A) sprays and that of the Pickering (C) sprays was 
observed. The results of the tests made on potatoes indicated that 
pei' unit. of copper present the Pickering sprays were twice as effec- 
tive as the Bordeaux mixture. No evidence, however, was found t<> 
substantiate the claims of Bedford and Pickering (3, 4) that they 
were from 12 t<> 15 times as efficient as the standard Bordeaux 
sprays. As l<>nu r as enough lime to combine with the copper was 
present, the reduction of the lime content of Bordeaux sprays did 
not alter their fungicidal value. 

[ncreased yields of tubers were obtained on plats of potatoes 
treated with Bordeaux and with the stronger Pickering sprays, in- 



PICKERING SPRAYS. 45 

dicating that these sprays exerted similar stimulating and protec- 
tive action on potato plants. 

The adhesive properties of Pickering sprays varied with the 
foliage to which they were applied. They adhered to potato and 
cranberry leaves in practically the same degree as the standard 
Bordeaux, to apple leaves in a somewhat higher proportion, and to 
grape leaves in a lower proportion. 

No injurious effects followed the application of Pickering sprays 
to potatoes in Maine or to cranberries in New Jersey. The sprays, 
however, proved to be too caustic for use on the apple in Virginia or 
on grapes in New Jersey and Virginia. Pickering sprays can not be 
used on tender foliage. 

Barium-water sprays of the Pickering type, made with barium 
hydrate instead of lime and containing 0.7 per cent of copper sul- 
phate, proved very successful as a fungicide for potatoes. Such a 
spray containing 0.6 per cent of copper sulphate did not injure the 
foliage or fruit of the apple tree. 

These results are presented as the basis for further studies to be 
conducted in various parts of the country. It is believed that from 
this material agricultural experiment stations and other agencies 
will be able to devise formulas for sprays for certain crops contain- 
ing less copper sulphate than standard Bordeaux, which will prove 
just as effective as the more expensive spray. 



BIBLIOGRAPHY. 

I) Barker, B. T. P., and Giminoham, C. T. 

The fungicidal action of Bordeaux mixtures. J. Agr. Sri., vol. 4, pp. 76-94. 
Maw 1911. 

2 ) • ' 

Further observations on the Fungicidal action of Bordeaux mixtures. J. Agr. 
Sci . vol. 6, pp. 220-232. May, I'M I. 
3 Bedford, Dukeof, and Pickering, S. U. 

Bordeaux mixture. 8th Rept. Woburn Exp. Fruit Farm, pp. 1-127. 1908. 

4) . 

Copper fungicides. 11th Rept. YVobum Exp. Fruit Farm. pp. 1-191. 1910. 

5) Bell, J. M., ami Tamer, W. C. 

The action of lime in excess on copper sulphate solutions. J. Phvs. Chem., 
vol. 11, pp. 632-636. Nov.. 1<><)7. 

6) Bun ri:. (>. 

Bordeaux mixture: F Physico-chemical studies. Phytopathology, vol. 4, pp. 
125-180. June, 1914. 

7 > ■ 

Methods ot preparation and relative value of Bordeaux mixtures. N. H. Agr. 

Exp. Sta. Scientific Contribution 9, pp. 1-12. 1916. 

8) Clark. .1. 1". 

On the toxic properties of some copper compounds, with special reference to 
Bordeaux ndxture. Botan. Gaz., vol. 33, pp. 26-48. Jan., 1902. 

9) De Castei la, F. 

Copper fun£ricides for vine diseases. J. Dept. Agr. Victoria, vol. 16, pp. 592- 
594. Oct., 1918. 

10i ClMINCUAM, C T. 

The action of carhon dioxide on Bordeaux mixtures. J. Agr. Sci., vol. 4, pp. 
69-75. May, 1911. 

II) Girard, A. 

Recherches sur l'adherence aux feuilles des plantes, et notamment aux feuilles 
de la pomme de terre, des composes cuivriques destines a combattre leur 
maladies. Compt. rend., vol. 114, pp. 234-236. Feb., 1892. 

12) Hawkins, L. A. 

Some factors influencing the efficiencv of Bordeaux mixture. TJ. S. Dept. 
Agr., B. P. J. Bull. 265. Dec, 1912* 

13) LlJTMAN, B. F. 

The covering power of the precipitation membranes of Bordeaux mixture. 
PhvtopathuWv, vol. 2, pp. 32-11. Feb., 1912. 

14) .* 

Some studies on Bordeaux mixture. Yt. Agr. Exp. Sta. Bull. 196. March, 

L916. 
L5 McAlpini . 1» 

Limewater Bordeaux for spraying. J. Dept. Agr. Victoria, vol. 8, pp. 728-732. 

Nov., 1910. 

I'. I I8TEBHOTJT, \Y. J. V. 

Specific action of barium. Am. J. Botanv, vol. ?>, pp. 4S1-482. Nov., 1916. 
17) Pl( KERING, 8. Q. 

The interaction of metallic sulphates and caustic alkalis. J. Chem. Soc, vol 
91, pt. 2, pp. 1981-1988. 1907. 



L8) 
L9) 



The chemistry of Bordeaux mixture. J. Chem. Soc, vol. 91, pt. 2, pp. 1988- 
2001. 1907. 



Bordeaux spraying. .1. Alt. Sci., vol. :'>, pp. 171-178. Oct., 1909. 



The constitution of basic salts. .1. Chem. Soc, vol. 97, pt. 2, pp. 1S51-1860. 
1910. 

46 



PICKERING SPRAYS. 47 

<21) Pickering, S. U. 

Copper fungicides. J. Agr. Sci., vol. 4, pp. 273-281. Jan., 1912. 

(22) Sicard, L. 

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